Elective cryopreservation of all embryos with subsequent cryothaw embryo transfer in patients at risk for ovarian hyperstimulation syndrome reduces the risk of adverse obstetric outcomes: a preliminary study

Untangling the independent effect of endometriosis, adenomyosis, and ART-related factors on maternal, placental, fetal, and neonatal adverse outcomes: results from a systematic review and meta-analysis

BACKGROUND

Women with endometriosis may constitute a group at a particularly increased risk of pregnancy-related complications. Furthermore, women selected for assisted reproductive technology (ART) are exposed to additional endocrinological and embryological factors that have been associated with adverse pregnancy outcomes.

OBJECTIVE AND RATIONALE

This study aimed to investigate the independent effect of endometriosis, adenomyosis, and various ART-related factors on adverse maternal, placental, fetal, and neonatal outcomes.

SEARCH METHODS

Published randomized controlled trials, cohort studies, and case-control studies were considered eligible. PubMed, MEDLINE, ClinicalTrials.gov, Embase, and Scopus were systematically searched up to 1 March 2024. This systematic review and meta-analysis was performed in line with the PRISMA and the MOOSE reporting guidelines. To thoroughly investigate the association between endometriosis/adenomyosis and adverse pregnancy outcomes, sub-analyses were conducted, whenever possible, according to: the method of conception (i.e. ART and non-ART conception), the endometriosis stage/phenotype, the coexistence of endometriosis and adenomyosis, any pre-pregnancy surgical treatment of endometriosis, and the form of adenomyosis. The odds ratio (OR) with 95% CI was used as effect measure. The quality of evidence was assessed using the GRADE approach.

OUTCOMES

We showed a higher risk of placenta previa in women with endometriosis compared to controls (34 studies, OR 2.84; 95% CI: 2.47, 3.26; I2 = 83%, moderate quality). The association was observed regardless of the method of conception and was particularly strong in the most severe forms of endometriosis (i.e. rASRM stage III-IV endometriosis and deep endometriosis (DE)) (OR 6.61; 95% CI: 2.08, 20.98; I2 = 66% and OR 14.54; 95% CI: 3.67, 57.67; I2 = 54%, respectively). We also showed an association, regardless of the method of conception, between endometriosis and: (i) preterm birth (PTB) (43 studies, OR 1.43; 95% CI: 1.32, 1.56; I2 = 89%, low quality) and (ii) cesarean section (29 studies, OR 1.52; 95% CI: 1.41, 1.63; I2 = 93%, low quality). The most severe forms of endometriosis were strongly associated with PTB. Two outcomes were associated with adenomyosis both in the main analysis and in the sub-analysis that included only ART pregnancies: (i) miscarriage (14 studies, OR 1.83; 95% CI: 1.53, 2.18; I2 = 72%, low quality) and (ii) pre-eclampsia (7 studies, OR 1.70; 95% CI: 1.16, 2.48; I2 = 77%, low quality). Regarding ART-related factors, the following associations were observed in the main analysis and confirmed in all sub-analyses conducted by pooling only risk estimates adjusted for covariates: (i) blastocyst stage embryo transfer (ET) and monozygotic twinning (28 studies, OR 2.05; 95% CI, 1.72, 2.45; I2 = 72%, low quality), (ii) frozen embryo transfer (FET) and (reduced risk of) small for gestational age (21 studies, OR 0.59; 95% CI, 0.57, 0.61; P < 0.00001; I2 = 17%, very low quality) and (increased risk of) large for gestational age (16 studies, OR 1.70; 95% CI, 1.60, 1.80; P < 0.00001; I2 = 55%, very low quality), (iii) artificial cycle (AC)-FET and pre-eclampsia (12 studies, OR 2.14; 95% CI: 1.91-2.39; I2 = 9%, low quality), PTB (21 studies, OR 1.24; 95% CI 1.15, 1.34; P < 0.0001; I2 = 50%, low quality), cesarean section (15 studies, OR 1.59; 95% CI 1.49, 1.70; P < 0.00001; I2 = 67%, very low quality) and post-partum hemorrhage (6 studies, OR 2.43; 95% CI 2.11, 2.81; P < 0.00001; I2 = 15%, very low quality).

WIDER IMPLICATIONS

Severe endometriosis (i.e. rASRM stage III-IV endometriosis, DE) constitutes a considerable risk factor for placenta previa and PTB. Herein, we recommend against superimposing on this condition other exposure factors that have a strong association with the same obstetric adverse outcome or with different outcomes which, if coexisting, could determine the onset of an ominous obstetric syndrome. Specifically, we strongly discourage the use of AC regimens for FET in ovulatory women with rASRM stage III-IV endometriosis or DE. We also recommend single ET at the blastocyst stage in this high-risk population.

REGISTRATION NUMBER

CRD42023401428.

Predicting the probability of a live birth after a freeze-all based in vitro fertilization-embryo transfer (IVF-ET) treatment strategy

BACKGROUND

The predictors for live birth rate (LBR) following one episode of in vitro fertilization (IVF) cycle for patients using a "freeze-all" strategy are not entirely clear.

METHODS

A retrospective cohort study utilizing a prediction model was developed to assess the relationship to the LBR. Women undergoing IVF with a freeze-all strategy were screened. Univariate models were first fitted for female age at oocytes retrieval/frozen-thawed embryo transfer (FET), body mass index (BMI), duration and etiology of infertility, previous IVF failures, total dose and duration of gonadotrophin, ovarian sensitivity index (OSI), number of oocytes collected, method of fertilization, number of embryos created, number and stage of embryos frozen, type and number of FET cycles, endometrial thickness (EMT)/pattern, hormone level on transplantation day, storage duration, number of embryos thawed and damaged thawed embryos, number and stage of embryos transferred and number of different quality embryos transferred. Variables with P<0.05 in the univariate model were selected for further analysis of the final multivariate discrete-time logistic regression model.

RESULTS

A total of 7,602 women undergoing one ovarian stimulation resulted in 9,964 FETs, of whom 3,066 (40.33%) had a live-birth after their first FET and 3,929 (51.68%) after total FETs. The EMT and woman's age at oocyte retrieval were the most important predictors. In the first FET, the LBR of women with an EMT ≤8 mm [27.40%; 95% confidence interval (CI): (21.60-33.81%)] was significantly lower than that of women with EMT between 9 and 11 mm [36.51%; 95% CI: (34.25-38.81%)] and thicker than 12 mm [44.23%; 95% CI: (42.22-46.25%)] (P<0.05). The optimistic and conservative cumulative LBRs of women younger than 31 years [87.5%; 95% CI: (86.32-88.61%) and 63.04%; 95% CI: (61.36-64.69%)] were significantly decreased in women aged 31-35, 36-40 and >40 (P<0.001).

CONCLUSIONS

Our study provides an effective prediction model for a woman's chance of having a baby after a "freeze-all" policy. The use of EMT and female age as tools to identify LBR are shown to be justified, and repeated FETs cannot reverse the age-dependent decline in fertility.

Maternal and obstetric outcomes are influenced by developmental stage and cryopreservation of transferred embryos after clomiphene citrate-based minimal stimulation IVF

STUDY QUESTION

Is the embryo transfer (ET) method associated with maternal and perinatal outcomes after minimal stimulation IVF using clomiphene citrate (CC)?

SUMMARY ANSWER

The incidence of pregnancy complications and adverse perinatal outcomes was influenced by the developmental stage (cleavage versus blastocyst stages) and cryopreservation (fresh versus vitrified) of the transferred embryos.

WHAT IS KNOWN ALREADY

Pregnancies resulting from IVF are associated with higher risks of adverse perinatal outcomes compared to natural conceptions; therefore, the next focus in reproductive medicine should be to assess whether these increased risks are attributable to IVF. Pregnancy complications and perinatal outcomes should be considered in addition to pregnancy outcomes when selecting the ET method, however, studies that describe the influence of transfer methods on perinatal and maternal outcomes are limited.

STUDY DESIGN, SIZE, DURATION

This study retrospectively analysed a large single-centre cohort. The clinical records of 36 827 women who underwent oocyte retrieval (during a CC-based minimal stimulation cycle) followed by their first ET at the fertility treatment centre between January 2008 and December 2017 were retrospectively analysed. The patients underwent a single fresh cleavage-stage ET (SFCT), single vitrified-warmed cleavage-stage ET (SVCT) or single vitrified-warmed blastocyst transfer (SVBT). This study only included one cycle per patient.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Oocyte retrieval was performed following CC-based minimal ovarian stimulation. The embryos were transferred 2–3 days after retrieval or vitrified at the cleavage or blastocyst stage. The vitrified embryos were then warmed and transferred within the natural cycles. Pregnancy complications and perinatal outcomes were stratified according to the transfer methods used. Multivariate logistic regression analysis was performed to evaluate the effect of ET methods on the prevalence of pregnancy complications and congenital anomalies.

MAIN RESULTS AND THE ROLE OF CHANCE

The rates of clinical pregnancy and delivery were significantly different among the groups. We analysed pregnancy complications in 7502 singleton births (SFCT, 3395 cycles; SVCT, 586 cycles; and SVBT, 3521 cycles). Multivariate logistic regression analysis revealed that the adjusted odds ratio (AOR) for hypertensive disorders in pregnancy was significantly lower in the SVBT group than in the SFCT group [AOR, 0.72; 95% CI, 0.56–0.92]. The AOR for low-lying placenta was lower in the SVBT group than in the SFCT group (AOR, 0.34; 95% CI, 0.19–0.60). The AOR for placenta previa was lower in the SVCT and SVBT groups than in the SFCT group (AOR, 0.21; 95% CI, 0.07–0.58 versus AOR, 0.53; 95% CI, 0.38–0.75, respectively). A total of 7460 follow-up data on neonatal outcomes was analysed. The AOR for preterm delivery was lower in the SVBT group than in the SFCT group (AOR, 0.78; 95% CI, 0.64–0.94). The AOR for low birthweight was significantly lower after SVCT and SVBT than after SFCT (AOR, 0.68; 95% CI, 0.46–0.98 versus AOR, 0.57; 95% CI, 0.48–0.66, respectively). The AOR for small for gestational age was lower in the SVCT and SVBT groups than in the SFCT group (AOR, 0.68; 95% CI, 0.46–0.98 versus AOR, 0.44; 95% CI, 0.36–0.55, respectively). The AOR for large for gestational age babies was higher in the SVBT group than in the SFCT group (AOR, 1.88; 95% CI, 1.62–2.18). The incidence of each congenital anomaly was similar among the groups.

LIMITATIONS, REASONS FOR CAUTION

The study data were collected through self-reported parental questionnaires on maternal and neonatal outcomes. Our findings were not compared with the incidence of pregnancy complications and congenital anomalies in natural pregnancies. Furthermore, this study was retrospective in nature; therefore, further studies are required to ascertain the generalizability of these findings to other clinics with different protocols and/or different patient demographics.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrated reassuring outcomes for SVBT (in terms of a lower incidence of pregnancy complications) compared to SFCT. Our findings provide valuable knowledge that will help improve perinatal and maternal outcomes in CC-based stimulation and inform couples of the possible benefits and risks of each type of ET method.

STUDY FUNDING/COMPETING INTEREST(S)

This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Placenta Accreta Spectrum: In Vitro Fertilization and Non-In Vitro Fertilization and Placenta Accreta Spectrum in a Massachusetts Cohort

OBJECTIVE

The incidence of placenta accreta spectrum (PAS) has been increasing in the United States. In addition, there has also been an increase in the utilization of in vitro fertilization (IVF). The IVF pregnancies confer an increased risk of adverse obstetric and neonatal outcomes, but there is limited data on whether IVF is associated with PAS. The aim of this study is to assess the association between IVF and the risk of PAS.

STUDY DESIGN

This was a retrospective cohort study of deliveries from January 1, 2013 to August 1, 2018 at a tertiary hospital in the Massachusetts. IVF pregnancies were compared with non-IVF pregnancies, and PAS diagnosis was confirmed by histopathology reports. Hospital administrative data and medical record review were used, and supplemented with data from birth certificates from the Massachusetts Department of Public Health.

RESULTS

We identified 28,344 pregnancies that met inclusion criteria, of which 1,418 (5.0%) were IVF pregnancies. The overall incidence of PAS was 0.4% (2.2% in the IVF group and 0.3% in the non-IVF group). Women who underwent IVF had 5.5 times the risk of PAS (95% confidence interval [CI]: 3.4-8.7) compared with women in the non-IVF group, adjusted for maternal age, nulliparity, and year of delivery (Table 5). Compared with women in the non-IVF group, the IVF group had fewer prior cesarean deliveries (22.6 vs. 64.2%) and a lower prevalence of placenta previa (19.4 vs. 44.4%).

CONCLUSION

Women with an IVF pregnancy carry an increased risk of PAS compared with non-IVF. Among women who underwent IVF, there was a lower prevalence of prior cesarean deliveries and placenta previa. Future work is needed to identify the mechanism of association for this increased risk as well as a reliable tool for antenatal detection in this cohort of women.

KEY POINTS

· IVF pregnancies have higher risk of PAS than non-IVF pregnancies.. · IVF pregnancies with PAS do not exhibit common risk factors.. · IVF may be an independent risk factor for PAS..

Supraphysiological estradiol levels on the hCG trigger day are associated with SGA for singletons born from fresh embryo transfer

The effects of supraphysiological estradiol (E2) on neonatal outcomes and the significance of specific E2 concentrations remain unclear. The purpose of this study was to investigate whether supraphysiological E2 levels on the human chorionic gonadotropin (hCG) trigger day are associated with small size for gestational age (SGA) in singletons born from fresh embryo transfer (ET) cycles. Patients with singleton pregnancies who delivered after the transfer of fresh embryos, during the period from July 2012 to December 2017, at our center were included. We excluded cycles involving a vanishing twin, maternal age >35 years, basal follicle-stimulating hormone ≥10 mIU/ml, or anti-Müllerian hormone ≤1 ng/ml. We then divided all cycles into five groups by E2 level on trigger day: group A, <2000 pg/ml (reference group); group B, 2000 pg/ml≤E2<2999 pg/ml; group C, 3000 pg/ml≤E2<3999 pg/ml; group D, 4000 pg/ml≤E2<4999 pg/ml; and group E, ≥5000 pg/ml. The prevalence of SGA among singletons from fresh ET was the primary outcome. The SGA rate significantly increased when the E2 level was ≥4000 pg/ml, as observed by comparing groups D (odds ratio [OR]: 1·79, 95% confidence interval [CI]: 1·16-2·76, P = 0·01) and E (OR: 1·68, 95% CI: 1·10-2·56, P = 0·02) with the reference group. Multivariate logistic regression indicated that a serum E2 level of at least 4000 pg/ml on the hCG trigger day was associated with increased SGA and with significant differences for groups D (adjusted OR [AOR]: 1·65, 95% CI: 1·05-2·59, P = 0·03) and E (AOR: 1·60, 95% CI: 1·03-2·53, P = 0·04) relative to the reference group. In conclusion, in fresh ET cycles, the supraphysiological E2 ≥4000 pg/ml on the hCG trigger day increases the risk of SGA.

Does contemporary ART lead to pre-eclampsia? A cohort study and meta-analysis

PURPOSE

Recent publications suggested that the risk for pre-eclampsia (PE) is higher with frozen-thawed embryo transfers (FETs) compared to fresh transfers (IVF-ETs). These studies were based on old data that reflects outdated practices. In this paper, we wanted to assess the incidence of PE in current assisted reproductive technology (ART) practice.

METHODS

In this cohort study, we present the incidence of PE in all births in the province of Ontario, Canada, for the years 2013-2017 for FET, IVF-ET, and natural conceptions (NC). We also compare our findings to previous studies in a meta-analysis that includes over 4 million births.

RESULTS

The results of our study show that contemporary practice of ART results in comparable risk for PE between FET and IVF-ET; however, the risk is higher than NC.

CONCLUSION

Current ART practice is associated with a lower risk for PE in frozen embryo transfer; this RR can be further attenuated by using ovulatory endometrial preparation for FETs.

Vanishing Twins Conceived Through Fresh In Vitro Fertilization: Obstetric Outcomes and Placental Pathology

OBJECTIVE

To characterize the obstetric outcomes and placental pathology in live births arising from vanishing twin pregnancies compared with nonreduced in vitro fertilization (IVF) pregnancies.

METHODS

This is a retrospective cohort study of live births resulting from fresh embryo transfers after IVF cycles with autologous oocytes from 2004 through 2017 at a large academic fertility center. Clinical information and pathology reports were reviewed. Placental diagnoses were coded using established nosology by expert placental pathologists. Analysis of variance, Kruskal-Wallis, Pearson's χ, and Fisher exact tests were used, as appropriate, to compare pathology categories between pregnancy outcomes. Mixed effects logistic regression models were generated to reveal the association between pregnancy outcome and placenta pathology, controlling for pregnancies arising in the same woman and various suspected confounders.

RESULTS

Of 905 fresh autologous IVF cycles with placental pathology available for review, we identified 73 vanishing twin pregnancies (8.1%), 556 singleton pregnancies (61.4%), and 276 twin pregnancies (30.5%). Vanishing twin syndrome was not associated with preterm delivery, route of delivery, growth restriction or other obstetric outcomes as compared with IVF singleton pregnancies. However, vanishing twin syndrome pregnancies showed distinctive placental pathologies including an increased rate of small placentas (less than the 10th percentile by weight), with more anatomical abnormalities than IVF singleton pregnancies (odds ratio 1.73, 95% CI 0.94-3.19; adjusted odds ratio 2.15, 95% CI 1.08-4.28). The frequency of placental vascular and inflammatory pathologies associated with IVF vanishing twin syndrome pregnancies were similar to that of IVF singleton pregnancies. Loss of a twin after 8 weeks of gestation was not associated with greater risks of placental pathologies.

CONCLUSION

In vitro fertilization pregnancies affected by vanishing twin syndrome did not have significant differences in obstetric or perinatal outcomes as compared with twin or singleton gestations. However, early twin loss was potentially associated with differences in placental development associated with a higher rate of small placentas and other anatomic pathologies.

Placental pathology in live births conceived with in vitro fertilization after fresh and frozen embryo transfer

BACKGROUND

The availability and use of frozen embryos after ovarian hyperstimulation for assisted reproduction has increased with improvement in vitrification techniques and the rise of preimplantation genetic testing. However, there are conflicting data regarding whether obstetric outcomes differ between fresh and frozen embryo transfer cycles.

OBJECTIVE

To compare placental pathology from live births arising from fresh and frozen embryo transfer cycles.

MATERIALS AND METHODS

A cohort of 1140 live births with placental pathology arising from autologous in vitro fertilization cycles with fresh or frozen programmed transfer performed at MGH Fertility Center between 2004 and 2017 was retrospectively reviewed. An experienced placental pathologist categorized the reported placental pathology as anatomic, infectious, inflammatory, or vascular/thrombotic. Our primary outcomes were differences in these placental pathologies between the 2 groups. Patient demographic, cycle, and birth outcomes were compared with the use of χ² tests, Student t test, or nonparametric tests, as appropriate. Multivariate logistic regression models were used to compare placental pathology between the fresh and frozen transfer groups.

RESULTS

Of the 1140 cycles included in our analysis, 929 arose from fresh embryo transfers (81.3%) and 211 arose from programmed frozen embryo transfers (18.5%). For both transfer types, the average age of the women at time of treatment was 35 years; mean body mass indices were within the normal range (23.6 kg/m² for fresh transfers and 23.2 kg/m² for frozen transfers, P = .26), and mean day 3 follicle-stimulating hormone values were 7.1 and 7.0 IU/L (P = .44), respectively. Deliveries occurred on average at 37.5 and 38.0 weeks' gestational age (P = .04) in the fresh versus frozen transfer group, with similar rates of obstetric complications. However, frozen transfers were more likely to be associated with marginal cord insertion (adjusted odds ratio, 1.87; confidence interval, 1.21, 2.91; P = .01), accessory lobe formation (adjusted odds ratio, 2.96; confidence interval, 1.12, 7.79; P = 0.03), subchorionic thrombi (adjusted odds ratio, 3.72; confidence interval, 1.80, 7.71; P < .001), and fetal vascular malperfusion characteristics with cord anomalies (adjusted odds ratio, 2.34; confidence interval, 1.22, 4.46; P = .01). These trends persisted when we analyzed day 5 transfers alone, and single frozen embryo transfers remained associated with increased rates of subchorionic thrombi compared to single fresh embryo transfers.

CONCLUSION

Pregnancies arising from frozen embryo transfers demonstrated more anatomic and vascular placental pathology than those from fresh transfers in our cohort of patients, despite similar maternal outcomes. More research is needed to explore how these differences in pathology may influence obstetric and perinatal outcomes.

Pregnancy and perinatal outcomes in pregnancies resulting from time interval between a freeze-all cycle and a subsequent frozen-thawed single blastocyst transfer

Background

Adverse obstetric outcomes are correlated with altered circulating hormone levels at the time implantation by the trophectoderm. What’ more, embryo freezing process may also have adverse effect on perinatal outcomes. This study aims to evaluate whether increasing interval time between a freeze-all cycle and a subsequent frozen-thawed single blastocyst transfer could have any effect on pregnancy and perinatal outcomes.

Methods

This was a retrospective cohort study included the first single blastocyst transfer in artificially cycles of all patients who underwent a freeze-all cycle between January 1^st, 2016 and September 30^th, 2018. All patients were divided into two groups according to the time interval between oocyte retrieval and the day of first frozen-thawed embryo transferred (FET): Group 1 (immediate FET cycles) and Group 2 (delayed FET cycles).

Results

No significant differences were reported between the two groups regarding the rates of clinical pregnancy, live birth, biochemical pregnancy and pregnancy loss even after adjusting for measured confounding. When accounting for perinatal outcomes, gestational age, birth weight, delivery mode, fetus gender, preterm birth, gestational hypertension, GDM, placenta previa, fetal malformation and low birthweight also did not vary significantly between the two groups. Only the incidence of macrosomia was more frequently in the Group 2 compared with the Group 1 (AOR 3.886, 95%CI 1.153–13.103, P = 0.029) after adjusting with a multiple logistic regression model.

Conclusions

We found delayed FET cycles for blastocyst transfer following freeze-all cycles may not improve the pregnancy outcomes. On the contrary, postponement of FET cycles may increase the risk of macrosomia. Therefore, FET cycles for blastocyst transfer should be done immediately to avoid adverse effects of delayed time on perinatal outcomes.

Increased blood pressure and impaired endothelial function after accelerated growth in IVF/ICSI children

STUDY QUESTION

What is the effect of growth velocity (height and weight) in early infancy on metabolic end-points and endothelial function in children born after ART?

SUMMARY ANSWER

Neonatal, infant and childhood growth is positively related to blood pressure in 9-year-old IVF/ICSI offspring, while growth in childhood was negatively associated with endothelial function.

WHAT IS KNOWN ALREADY

Offspring of pregnancies conceived after ART are at risk for later cardiometabolic risk factors. It is well established that early growth is related to numerous later cardiometabolic risk factors such as high blood pressure. This concept is known as the Developmental Origin of Health and Disease theory.

STUDY DESIGN SIZE DURATION

The relation between early growth and later cardiometabolic risk profile was studied in the MEDIUM-KIDS study, a prospective observational cohort study in children born after an IVF/ICSI treatment. In 131 children (48.1% males) at the average age of 9.4 years, cardiometabolic outcomes were assessed and growth data from birth until age 9 years were collected from child welfare centers.

PARTICIPANTS/MATERIALS SETTINGS METHODS

The following cardiometabolic outcomes were assessed: blood pressure, skinfolds, lipid spectrum, hair cortisone and glucose and insulin levels. Data on maximum skin perfusion after transdermal delivery of acetylcholine as a measure of endothelial function were collected.Growth charts were obtained electronically from child welfare centers, which offer free consultations and vaccinations to all Dutch children. At these centers, height and weight are recorded at predefined ages. Growth was defined as z-score difference in weight between two time points. Multivariable linear regression analysis was used to model the relation between growth and cardiometabolic outcomes. The following growth windows were -studied simultaneously in each model: 0-1 month, 1-3 months, 3-6 months, 6-11 months, 11-24 months and 2-6 years. The model was adjusted for height growth in all intervals except for 0-1 month.

MAIN RESULTS AND THE ROLE OF CHANCE

In multivariable linear regression analyses, multiple growth windows were positively associated with blood pressure, for example growth from 2-6 years was significantly related to systolic blood pressure: B = 4.13, P = 0.005. Maximum skin perfusion after acetylcholine was negatively associated with height-adjusted weight gain from 2 to 6 years: B = -0.09 (log scale), P = 0.03. Several growth windows (weight 1-3 months, 3-6 months, 6-11 months, 11-24 months, 2-6 years) were positively linked with total adiposity. Lipids, glucose tolerance indices and cortisone were not related to growth.

LIMITATIONS REASONS FOR CAUTION

This study is of modest size and of observational nature, and we did not include a control group. Therefore, we cannot assess whether the observed associations are causal. It is also not possible to analyze if our observations are specific for, or exacerbated in, the ART population. Ideally, a control group of naturally conceived siblings of IVF/ICSI children should simultaneously be studied to address this limitation and to assess the impact of the ART procedure without the influence of parental (subfertility) characteristics.

WIDER IMPLICATIONS OF THE FINDINGS

The results of this study contribute to our understanding of the reported increased risk for hypertension in ART offspring. We speculate that early, accelerated growth may be involved in the reported increased risk for hypertension in ART offspring, with endothelial dysfunction as a possible underlying mechanism. However, additional research into the mechanisms involved is required.

STUDY FUNDING/COMPETING INTERESTS

The study was financially supported by the March of Dimes, grant number #6-FY13-153. The sponsor of the study had no role in study design, data collection, data analysis, data interpretation or writing of the paper. The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

NTR4220.

Could ethnicity have a different effect on fresh and frozen embryo transfer outcomes: a retrospective study

RESEARCH QUESTION

Does a woman's ethnicity affect her fresh and frozen embryo transfer outcomes differently?

DESIGN

A retrospective cohort study of the first fresh and first frozen embryo transfer per woman carried out at a single tertiary level fertility unit between 2010 and 2016 using data retrieved from an electronic database. Biochemical pregnancy, biochemical pregnancy loss, clinical pregnancy, miscarriage and live birth rates per embryo transfer were compared between 5876 white Caucasian, 1071 South Asian and 114 Black Afro-Caribbean women undergoing their first fresh embryo transfer and for 1418 Caucasian, 273 South Asian and 31 Afro-Caribbean women undergoing their first frozen embryo transfer. Logistic regression was used to adjust for age, number of oocytes retrieved, and number and stage of embryos transferred.

RESULTS

South Asian (26% versus 32%, adjusted OR 0.622, 95% CI 0.533 to 0.725) and Black Afro-Caribbean women (21% versus 32%, adjusted OR 0.528, 95% CI 0.332 to 0.839) had a lower live birth rate per fresh embryo transfer compared with white Caucasian women. In contrast, the live birth rates per frozen embryo transfer were not significantly different between South Asian and Caucasian women (26% versus 28%, adjusted OR 0.890, 95% CI 0.661 to 1.200) and between Afro-Caribbean and Caucasian women (29% versus 28%, adjusted OR 0.983, 95% CI 0.447 to 2.162).

CONCLUSION

South Asian and Black Afro-Caribbean women have a significantly lower live birth rate than white Caucasian women after fresh embryo transfer, but their frozen embryo transfer live birth rates are not significantly different.

The placental transcriptome of the first-trimester placenta is affected by in vitro fertilization and embryo transfer

BACKGROUND

The placenta is a highly specialized temporary organ that is related to fetal development and pregnancy outcomes, and epidemiological data demonstrate an increased risk of placental abnormality after in vitro fertilization and embryo transfer (IVF-ET).

METHODS

This study examines alterations in the transcriptome profile of first-trimester placentas from IVF-ET pregnancies and analyzes the potential mechanisms that play a role in the adverse perinatal outcomes associated with IVF-ET procedures. Four human placental villi from first-trimester samples were obtained through fetal bud aspiration from patients subjected to IVF-ET due to oviductal factors. An additional four control human placental villi were derived from a group of subjects who spontaneously conceived a twin pregnancy. We analyzed their transcriptomes by microarray. Then, RT-qPCR and immunohistochemistry were utilized to analyze several dysregulated genes to validate the microarray results. Biological functions and pathways were analyzed with bioinformatics tools.

RESULTS

A total of 3405 differentially regulated genes were identified as significantly dysregulated (> 2-fold change; P < 0.05) in the IVF-ET placenta in the first trimester: 1910 upregulated and 1495 downregulated genes. Functional enrichment analysis of the differentially regulated genes demonstrated that the genes were involved in more than 50 biological processes and pathways that have been shown to play important roles in the first trimester in vivo. These pathways can be clustered into coagulation cascades, immune response, transmembrane signaling, metabolism, cell cycle, stress control, invasion and vascularization. Nearly the same number of up- and downregulated genes participate in the same biological processes related to placental development and maintenance. Procedures utilized in IVF-ET altered the expression of first-trimester placental genes that are critical to these biological processes and triggered a compensatory mechanism during early implantation in vivo.

CONCLUSION

These data provide a potential basis for further analysis of the higher frequency of adverse perinatal outcomes following IVF-ET, with the ultimate goal of developing safer IVF-ET protocols.

Vascular Endothelial Growth Factor Delivery to Placental Basal Plate Promotes Uterine Artery Remodeling in the Primate

Extravillous trophoblast (EVT) uterine artery remodeling (UAR) promotes placental blood flow, but UAR regulation is unproven. Elevating estradiol (E2) in early baboon pregnancy suppressed UAR and EVT vascular endothelial growth factor (VEGF) expression, but this did not prove that VEGF mediated this process. Therefore, our primate model of prematurely elevating E2 and contrast-enhanced ultrasound cavitation of microbubble (MB) carriers was used to deliver VEGF DNA to the placental basal plate (PBP) to establish the role of VEGF in UAR. Baboons were treated on days 25 to 59 of gestation (term, 184 days) with E2 alone or with E2 plus VEGF DNA-conjugated MBs briefly infused via a maternal peripheral vein on days 25, 35, 45, and 55. At each of these times an ultrasound beam was directed to the PBP to collapse the MBs and release VEGF DNA. VEGF DNA-labeled MBs per contrast agent was localized in the PBP but not the fetus. Remodeling of uterine arteries >25 µm in diameter on day 60 was 75% lower (P < 0.001) in E2-treated (7% ± 2%) than in untreated baboons (30% ± 4%) and was restored to normal by E2/VEGF. VEGF protein levels (signals/nuclear area) within the PBP were twofold lower (P < 0.01) in E2-treated (4.2 ± 0.9) than in untreated (9.8 ± 2.8) baboons and restored to normal by E2/VEGF (11.9 ± 1.6), substantiating VEGF transfection. Thus, VEGF gene delivery selectively to the PBP prevented the decrease in UAR elicited by prematurely elevating E2 levels, establishing the role of VEGF in regulating UAR in vivo during primate pregnancy.

Infertility: a marker of future health risk in women?

Infertility, may be a harbinger for future health risk in women, including early mortality. Fertility status itself could serve as an early biomarker, (present in a woman's reproductive years) for risk stratification later in life. The relationship between infertility and early mortality involves the impact of nulliparity on future adverse health events, potential sequelae from the underlying cause(s) of infertility, the risks of fertility treatments, as well as the potential for risk reduction from a healthy pregnancy. This complex interplay coupled with difficulties ascertaining infertility on a population level has presented unique challenges to assessing infertility and early mortality risk. With further study, a better understanding the role of fertility status in health at various stages of life may provide unique opportunities for surveillance and risk reduction.

Effects of Supraphysiologic Levels of Estradiol on Endometrial Decidualization, sFlt1, and HOXA10 Expression

OBJECTIVE

Supraphysiologic estradiol (E₂) levels associated with controlled ovarian hyperstimulation in high in vitro fertilization (IVF) responders may alter implantation and placentation and increase the risk of preeclampsia. Our hypothesis is that elevated E₂ levels in vitro significantly alter endometrial decidualization, sFlt1, and HOXA10 expression.

METHODS

Human endometrial stromal cells were treated with a decidualization cocktail of medroxyprogesterone, cyclic adenosine monophosphate, and 3 concentrations of E₂ 10 nM (standard), 100 nM (intermediate), or 1000 nM E₂ (high). Effects on sFlt1, prolactin (PRL), insulin-like growth factor binding protein 1 (IGFBP-1), vascular endothelial growth factor (VEGF), and HOXA10 were studied.

RESULTS

Prolactin, IGFBP-1, and VEGF significantly increased at all 3 E₂ concentrations. While IGFBP-1 and VEGF did not change with increasing E₂, PRL was less with high E₂ (6.0 ng/mL ± 1.4 standard error of the mean) compared to standard (21.4 ± 3.2) and intermediate (19.8 ± 3.8). sFlt1 decrease was similar at all E₂ concentrations. HOXA10 was lower at standard (10%) and intermediate (30%) as expected, but did not change with high E₂.

CONCLUSIONS

Supraphysiologic E₂ levels associated with high IVF responders that exceed in vivo levels may impair in vitro endometrial decidualization. Although PRL did increase with high E₂, the levels were, however, attenuated and 3.4-fold lower than standard and intermediate E₂. sFlt1 was decreased under all 3 conditions with no differences between concentrations. Reduced HOXA10 was not observed with high E₂. These findings suggest that elevated E₂ levels in vitro may alter endometrial decidualization and subsequently affect implantation and placentation.

Risk of preeclampsia following assisted reproductive technology: systematic review and meta-analysis of 72 cohort studies

Objective: Previous studies have indicated that women with assisted reproductive technology (ART) pregnancy have an increased risk of preeclampsia. The aim of this current study was to estimate, through a systematic review and meta-analysis of cohort studies, the risk of preeclampsia in women who conceived with ART.Materials and methods: We searched ISI Web of Knowledge, Medline/PubMed, Scopus and Embase up to August 2017 for English-language articles pertaining to risk of preeclampsia in ART pregnancy using standard keywords. Data extraction was conducted by two authors and quality of the studies was assessed using the Newcastle-Ottawa Scale. A random-effects model was used for the meta-analysis.Results: In total, 72 cohort studies (n = 164 870) were included. The results of Cochran test and I² statistic indicated considerable heterogeneity among studies (Q = 15 415.61, df = 71, p < .001, I²=99.5%). The pooled estimate of preeclampsia risk using the random effects model was 10.8% (95% CI: 9.10-12.5). Furthermore, the funnel plot and Begg's test showed evidence of publication bias.Conclusions: We found that the risk of preeclampsia was very high among women who conceived with ART. Women should be counseled carefully before undergoing ART treatment.

Placental volume and other first-trimester outcomes: are there differences between fresh embryo transfer, frozen-thawed embryo transfer and natural conception?

RESEARCH QUESTION

Does mode of conception influence placental volume and other first-trimester outcomes?

DESIGN

This retrospective single-centre case-control study led in Dijon University Hospital included 252 singleton pregnancies (84 IVF with either fresh embryo transfer or frozen-thawed embryo transfer [FET] and 168 natural conceptions). First-trimester placental volume, uterine artery pulsatility index and maternal serum PAPP-A and beta-HCG were measured. Statistical analyses were adjusted for gestational age, the newborn's gender, maternal age, parity, body mass index and smoking status.

RESULTS

Placental volume was significantly greater in the FET group than in the control group (P = 0.043) and fresh embryo transfer (P = 0.023) groups. At birth, fresh embryo transfer newborns were significantly smaller than controls (P = 0.01) and FET newborns (P = 0.008). Postpartum haemorrhage was far more frequent in FET than in controls and fresh embryo transfer group (38.1%, 2.6% and 1.9%, respectively; P < 0.0001). Placental volume positively correlated with PAPP-A, beta-HCG and the newborn's birth weight, and negatively correlated with uterine artery pulsatility index.

CONCLUSIONS

Placental volume and other first-trimester parameters are modified by IVF with fresh embryo transfer and FET compared with natural conception, but with opposite trends. Given the different protocols used for these techniques, hormonal treatment per se may have a major effect on pregnancy outcomes through the modification of placental invasiveness.

Evaluating the benefit of measuring serum progesterone prior to the administration of HCG: effect of the duration of late-follicular elevated progesterone following ovarian stimulation on fresh embryo transfer live birth rates

RESEARCH QUESTION

Progesterone overproduction during ovarian stimulation is associated with lower live birth rates (LBR) after fresh embryo transfer. Therefore, circulating P concentrations on the day of HCG administration are frequently measured in clinical practice and followed by an elective cryopreservation strategy whenever late-follicular elevated P (LFEP) occurs. A recent study concluded that the duration of LFEP >1.00 ng/mL prior to HCG administration may also affect clinical pregnancy rates. The objective of this current study was to assess whether this hypothesis was reproducible using LBR as the primary outcome.

DESIGN

Retrospective analysis including women undergoing IVF/ICSI between 2010-2015. LBR were compared among different P elevation duration subgroups (0, 1 or >1 day) using two LFEP thresholds (>1.00 ng/mL and >1.50 ng/mL).

RESULTS

The duration of LFEP >1.00 ng/mL was not associated with a significant decrease in LBR according to whether the patient had LFEP lasting for 0, 1 or >1 days (29.9%, 30.3% and 26.3%, respectively). Conversely, when using >1.50 ng/mL as the LFEP threshold, LBR decreased significantly (30.3% 20.4% and 20.5%, respectively). However, the relative frequency of having LFEP >1.50 ng/mL for >1 day was exceedingly rare (1.9%) and the additional benefit of evaluating LFEP beyond the day of HCG triggering no longer remained statistically significant after confounder-adjustment with multivariable regression analysis.

CONCLUSION

These results suggest a lack of benefit in measuring serum P in the days preceding HCG administration, since LBR in women with LFEP >1 day do not vary significantly from those with LFEP detected only on the day of HCG administration.

Müllerian-Inhibiting Substance/Anti-Müllerian Hormone as a Predictor of Preterm Birth in Polycystic Ovary Syndrome

CONTEXT

There is increasing evidence for Müllerian-inhibiting substance (MIS)/anti-Müllerian hormone (AMH) physiologic activity in the human uterus, so it is relevant to study how MIS/AMH levels impact pregnancy.

OBJECTIVE

To investigate the association of MIS/AMH levels with the risk of adverse obstetric outcomes.

DESIGN

Retrospective cohort study.

SETTING

Academic fertility center.

PATIENTS

Women who became pregnant through in vitro fertilization between January 2012 and October 2016. Exclusion criteria were: oocyte donation, gestational carrier, multiple gestations, miscarriage before 20 weeks, or medically indicated preterm deliveries.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

There were two primary outcomes, preterm birth and cesarean delivery for arrest of labor. Because MIS/AMH level is highly skewed by certain infertility diagnoses, the preterm birth analysis was stratified by polycystic ovary syndrome (PCOS) diagnosis, and the cesarean delivery for arrest of labor analysis was stratified by diminished ovarian reserve diagnosis. χ2, Mann-Whitney, and t tests were used as appropriate. A P value of <0.05 was considered statistically significant.

RESULTS

Among women with PCOS, those who delivered prematurely had substantially higher MIS/AMH levels (18 vs 6.4 ng/mL, P = 0.003) than did those who delivered at term. At the highest MIS/AMH values, preterm deliveries predominated; above the 90th percentile in women with PCOS, all deliveries were premature. No effect of MIS/AMH level was observed in women without PCOS. We found no association between MIS/AMH values and cesarean delivery for labor arrest.

CONCLUSION

In women with PCOS, substantially elevated MIS/AMH levels are significantly associated with preterm birth, suggesting closer follow-up and further studies to elucidate the underlying mechanisms.

Superovulation alters the expression of endometrial genes critical to tissue remodeling and placentation

PURPOSE

Epidemiologic data suggest that in vitro fertilization (IVF) is associated with an increased risk of disorders of placentation including preeclampsia and fetal growth restriction. Specifically, studies have demonstrated that singleton pregnancies conceived following a fresh embryo transfer are at an increased risk of delivering an infant with low birth weight compared to those conceived following a frozen embryo transfer. The mechanism responsible for this association remains unclear. Procedures utilized in IVF have also been linked with epigenetic changes and gene expression changes in both fetal and maternal tissues. Data suggest that modifications in the maternal endometrium can lead to disordered trophoblast invasion and placentation. This study examines the effect of ovarian stimulation on endometrial gene expression and DNA methylation during the window of implantation to examine potential pathways playing a role in the adverse outcomes associated with IVF.

METHODS

Endometrial biopsies were obtained from oocyte donors and age-matched naturally cycling women 11 days following oocyte retrieval in donors or 12 days following luteinizing hormone (LH) surge in naturally cycling women. Global gene expression was analyzed via Affymetrix Human Gene 1.1 ST array and confirmed with RT-qPCR. DNA methylation was assessed with the Infinium DNA methylation 450 K BeadChip.

RESULTS

Analysis of endometrial gene expression from 23 women (11 oocyte donors and 12 controls) demonstrated 165 genes with a greater than twofold change in expression between donors and controls. While there were 785 genes with significant differential methylation in the endometrium of donors when compared with control subjects, none of the genes with altered expression showed significant changes in DNA methylation. Analysis of the differentially expressed genes showed enrichment for genes involved in endometrial remodeling including PLAT, HSPE2, MMP2, and TIMP1. Validation studies using RT-qPCR found a 73% reduction in expression of heparanase 2 (HSPE2) an enzyme associated with both angiogenesis and cell invasion, a greater than twofold increase in tissue-type plasminogen activator (PLAT), a serine protease participating in matrix degradation, and a 70% increase in MMP2, a gelatinase involved in collagen and fibronectin breakdown.

CONCLUSIONS

Superovulation alters expression of genes critical to endometrial remodeling during early implantation. Such changes could lead to altered trophoblast migration and impaired endovascular invasion. These findings offer a potential mechanism for the adverse perinatal outcomes observed following embryo transfer during fresh IVF cycles.

Obstetric outcomes after fresh versus frozen-thawed embryo transfers: A systematic review and meta-analysis

Objective

To evaluate if there are differences in the risks of obstetric outcomes in IVF/ICSI singleton pregnancies when compared fresh to frozen-thawed embryo transfers (FET).

Methods

This was a systematic review and meta-analysis evaluating the obstetric outcomes in singleton pregnancies after FET and fresh embryo transfer. The outcomes included in this study were pregnancy-induced hypertension (PIH), pre-eclampsia, placenta previa, and placenta accreta.

Results

The search yielded 654 papers, 6 of which met the inclusion criteria and reported on obstetric outcomes. When comparing pregnancies that arose from FET or fresh embryo transfer, there was an increase in the risk of obstetric complications in pregnancies resulting from FET when compared to those emerging from fresh embryo transfers in PIH (aOR 1.82; 95% CI 1.24-2.68), pre-eclampsia (aOR 1.32, 95% CI 1.07, 1.63), and placenta accreta (aOR 3.51, 95% CI 2.04-6.05). There were no significant differences in the risk between the FET and fresh embryo transfer groups when evaluating placenta previa (aOR 0.70; 95% CI 0.46-1.08).

Conclusion

The obstetric outcomes observed in pregnancies arising from ART may differ among fresh and FET cycles. Thus, when evaluating to perform a fresh embryo transfer or a freeze-all cycle, these differences found in obstetric outcomes between fresh and FET should be taken into account. The adverse obstetric outcomes after FET found in this study emphasize that the freeze-all policy should not be offered to all the patients, but should be offered to those with a clear indication of the benefit of this strategy.

Risk of pre-eclampsia after fresh or frozen embryo transfer in patients undergoing oocyte donation

OBJECTIVES

Different perinatal and neonatal adverse outcomes have been reported to be increased in frozen embryo transfer pregnancies compared with fresh embryo transfer with patient's own oocytes. Concerning preeclampsia, it has also been reported to be increased after frozen embryo transfer. The objective of this study is to asses if there is an increased risk of preeclampsia and gestational hypertension in pregnancies achieved with oocyte donation after frozen embryo transfer compared to fresh embryo transfer.

STUDY DESIGN

Retrospective cohort study of 433 patients who underwent a cycle with donated oocytes either after fresh (n = 353) or frozen embryo transfer (n = 80) between March 2013 and April 2016 at a large fertility clinic. Participants are pregnant patients who reached the 20th week of gestation. The risk of preterm preeclampsia (presenting before 37 weeks of gestation), term preeclampsia (presenting at or after 37 weeks of gestation) and gestational hypertension are presented as unadjusted and adjusted odds ratio (OR).

RESULTS

Frozen embryo transfer have similar risk for developing preterm preeclampsia compared to fresh embryo transfer, with an OR of 1.95 (CI 95% 0.72, 5.26, p = 0.18), as well as term preeclampsia (OR 0.3, 95%CI 0.04, 2.35, p = 0.25), and gestational hypertension (OR 1.45, 95% CI 0.75, 2.81, P = 0.27).

CONCLUSIONS

Despite a high prevalence of preeclampsia in pregnancies achieved by oocyte donation, the freezing-thawing process does not confer more risk than the fresh embryo transfers in preterm preeclampsia, term preeclampsia or gestational hypertension.

The superovulated environment, independent of embryo vitrification, results in low birthweight in a mouse model

Epidemiological studies suggest that babies born following in vitro fertilization (IVF) and fresh embryo transfer are of lower birthweight than babies born following frozen embryo transfer, although the mechanism responsible for this phenotype is not known. We developed a novel mouse model that isolates the independent effects of embryo freezing and the superovulated environment, which cannot be performed in humans. We transferred blastocysts that had been vitrified and warmed, mixed with with fresh blastocysts, into individual pseudopregnant recipients produced by either natural mating or mating following injection with equine chorionic gonadotropin and human chorionic gonadotropin and hCG (superovulation). We found that superovulation of the recipient dams led to significantly lower fetal weight at term while blastocyst vitrification had no significant effect on fetal weight (1.43 ± 0.24 g fresh-natural, 1.30 ± 0.28 g vitrified-natural vs. 1.09 ± 0.20 fresh-superovulated, 0.93 ± 0.23 g vitrified-superovulated, P < 0.0001). Doppler ultrasound revealed increased median umbilical artery resistance in the placentae of near-term dams exposed to superovulation compared to naturally mated dams (0.927 vs 0.904, P = 0.02). Additionally, placental microvascular density was lower in superovulated compared to naturally mated dams (1.24 × 10-3 vessel/micron vs 1.46 × 10-3 vessels/micron, P = 0.046). Gene expression profiling suggested alterations in fetal genes involved in glucorticoid regulation. These results suggest a potential mechanism for altered birthweight following superovulation in our model and may have implications for human IVF.

Is frozen embryo transfer better for mothers and babies? Can cumulative meta-analysis provide a definitive answer?

BACKGROUND

Initial observational studies and a systematic review published 5 years ago have suggested that obstetric and perinatal outcomes are better in offspring conceived following frozen rather than fresh embryo transfers, with reduced risks of preterm birth, small for gestational age, low birth weight and pre-eclampsia. More recent primary studies are beginning to challenge some of these findings. We therefore conducted an updated systematic review and cumulative meta-analysis to examine if these results have remained consistent over time.

OBJECTIVE AND RATIONALE

The aim of this study was to perform a systematic review and cumulative meta-analysis (trend with time) of obstetric and perinatal complications in singleton pregnancies following the transfer of frozen thawed and fresh embryos generated through in-vitro fertilisation.

SEARCH METHODS

Data Sources from Medline, EMBASE, Cochrane Central Register of Clinical Trials DARE and CINAHL (1984-2016) were searched using appropriate key words. Observational and randomised studies comparing obstetric and perinatal outcomes in singleton pregnancies conceived through IVF using either fresh or frozen thawed embryos. Two independent reviewers extracted data in 2 × 2 tables and assessed the methodological quality of the relevant studies using CASP scoring. Both aggregated as well as cumulative meta-analysis was done using STATA.

OUTCOMES

Twenty-six studies met the inclusion criteria. Singleton babies conceived from frozen thawed embryos were at lower relative risk (RR) of preterm delivery (0.90; 95% CI 0.84-0.97) low birth weight (0.72; 95% CI 0.67-0.77) and small for gestational age (0.61; 95% CI 0.56-0.67) compared to those conceived from fresh embryo transfers, but faced an increased risk (RR) of hypertensive disorders of pregnancy (1.29; 95% CI 1.07-1.56) large for gestational age (1.54; 95% CI 1.48-1.61) and high birth weight (1.85; 95% CI 1.46-2.33). There was no difference in the risk of congenital anomalies and perinatal mortality between the two groups. The direction and magnitude of effect for these outcomes have remained virtually unchanged over time while the degree of precision has improved with the addition of data from newer studies.

WIDER IMPLICATIONS

The results of this cumulative meta-analysis confirm that the decreased risks of small for gestational age, low birth weight and preterm delivery and increased risks of large for gestational age and high birth weight associated with pregnancies conceived from frozen embryos have been consistent in terms of direction and magnitude of effect over several years, with increasing precision around the point estimates. Replication in a number of different populations has provided external validity for the results, for outcomes of birth weight and preterm delivery. Meanwhile, caution should be exercised about embarking on a policy of electively freezing all embryos in IVF as there are increased risks for large for gestational age babies and hypertensive disorders of pregnancy. Therefore, elective freezing should ideally be undertaken in specific cases such as ovarian hyperstimulation syndrome, fertility preservation or in the context of randomised trials.

Neonatal outcomes following fresh as compared to frozen/thawed embryo transfer in in vitro fertilization

In vitro fertilization (IVF) and embryo cryopreservation have become increasingly common in recent years. As utilization increases, it is important to understand the clinical effects these technologies have on offspring, as well as the mechanisms behind these effects. Many epidemiologic studies have observed that pregnancies following IVF are more likely to be affected by obstetric complications such as pre-eclampsia, preterm birth, and small for gestational age neonates compared with naturally conceived pregnancies. There has been a great deal of research emerging suggesting that these differences are related to the supraphysiologic hormonal environment that results from ovarian superovulation. While pregnancies resulting from frozen embryo transfer are less likely to experience these complications, babies born after frozen transfer are more likely to be large for gestational age. Epigenetic studies point toward differential methylation of genes critical for growth that may be responsible for the increased incidence of larger neonates following transfer of vitrified embryos. Although it does appear that perinatal outcomes are improved by transferring frozen embryos instead of fresh, it would be premature at this time to recommend universal freeze-all protocols in all patients. This article, as part of the "IVF Reviews" special issue of this journal, aims to expound on the issues outlined above.

Effect of next-generation sequencing in preimplantation genetic testing on live birth ratio

The present study analysed live birth ratios in frozen embryo transfer (FET) cycles where embryo ploidy status was determined with preimplantation genetic testing (PGT) using next-generation sequencing (NGS). PGT was performed on trophectoderm cells biopsied at the blastocyst stage. The present prospective cohort study included 112 women undergoing frozen embryo transfer, with NGS PGT. The control group consisted of 85 patients who underwent the IVF procedure with FET planned for a subsequent cycle. The live birth rate per cycle was higher by ~18.5 percentage points in the investigated compared with control group (42.0% vs 23.5% respectively; P = 0.012). The differences between the study and control groups were also significant for clinical pregnancy (42.0% vs 23.5% respectively; P = 0.012), implantation (41.2% vs 22.2% respectively; P = 0.001) and pregnancy loss rates (9.6% vs 28.6% respectively; P = 0.027). The results show that PGT NGS is a useful method for embryo selection and it may be implemented in routine clinical practice with propitious results.

Elective frozen-thawed embryo transfer (FET) in women at risk for ovarian hyperstimulation syndrome

Elective cryopreservation of cultured embryos has become a treatment option for women at risk for ovarian hyperstimulation syndrome (OHSS). The aim of our study was to investigate the outcome of elective cryopreservation and consecutive frozen-thawed embryo transfer (FET) in a large IVF clinic in Austria. A total of 6104 controlled ovarian hyperstimulation cycles (COH) were performed on 2998 patients including 200 patients (6.7%) who were undergoing elective cryopreservation and FET due to high risk of OHSS. We estimated the cumulative live birth rate using the Kaplan-Meier method and evaluated independent predictors for successful live births with a Cox model. A total of 270 frozen-thawed embryo transfers were performed on 200 patients with up to 4 transfers per patient. The first embryo transfer showed a live birth rate of 42.0%, the second transfer showed a cumulative rate of 58.5%. After a total of 4 FETs from the same COH cycle, a cumulative live birth rate of 61.0% per COH cycle could be achieved. Four cases of OHSS occurred amongst these patients (2.0%), all of them of moderate severity. Multivariate analysis identified maternal age, the use of assisted hatching and the number of embryos transferred at the blastocyst stage as independent predictors for cumulative live birth. Our study clearly suggests that elective FET is safe and shows excellent cumulative live birth rates. This concept can, therefore, be used to avoid the severe adverse events caused by COH and the inefficient use of cultured embryos.

Neutral effect of body mass index on implantation rate after frozen-thawed blastocyst transfer

OBJECTIVE

To examine the effects of body mass index (BMI) on implantation rate after uniform protocol frozen-thawed blastocyst transfer in women with a homogenous uterine environment.

DESIGN

Retrospective cohort study.

SETTING

Single IVF clinic at a large academic institution.

PATIENT(S)

Four hundred sixty-one infertile women treated at a large academic institution from January 2007 to January 2014.

INTERVENTION(S)

All women underwent standardized slow frozen-thawed blastocyst transfers with good-quality day 5-6 embryos, following an identical hormonal uterine preparation, with comparison groups divided according to BMI category: underweight (<18.5 kg/m²), normal weight (18.5-24.9 kg/m²), overweight (25.0-29.9 kg/m²), and obese (≥30.0 kg/m²).

MAIN OUTCOME MEASURE(S)

Implantation rate.

RESULT(S)

There were no statistically significant differences identified when comparing implantation rates among the four BMI cohorts. The implantation rate was 38.2% in normal weight patients, 41.7% in underweight patients, 45.1% in overweight patients, and 34.7% in obese patients. Adjusted odds ratios (OR) demonstrated no association between the main outcome, implantation rate, and BMI. Compared with the normal weight patients, the adjusted OR of implantation was 1.70 (95% confidence interval [CI], 0.40-7.72) for underweight patients, 1.61 (95% CI, 0.97-2.68) for overweight patients, and 0.92 (95% CI, 0.49-1.72) for obese patients. Secondary outcomes, including rates of miscarriage, clinical pregnancy, ongoing pregnancy, and live birth, were not significantly different between cohorts. While powered to detect a 16% difference between overweight and normal weight women, the study was underpowered to detect differences in the underweight and obese women, and no definitive conclusions can be drawn for these small cohorts. Patients with transfers that required the longest amount of time, greater than 200 seconds, had the highest average BMI of 27.5 kg/m².

CONCLUSION(S)

Under highly controlled circumstances across 7 years of data from a single institution, using a uniform uterine preparation, following a precise transfer technique with high-quality day 5-6 slow frozen-thawed blastocysts, a BMI in the overweight range of 25-29.9 kg/m² is not associated with a poorer implantation rate or live-birth rate, nor is it associated with an increased risk of miscarriage when compared with a normal BMI range. The increased length of time required during transfer for women with higher BMI suggests body habitus may contribute to difficult transfers, although this may not translate into poorer implantation rates. By using a standardized protocol for slow freezing and thawing of embryos, using identical hormonal preparation and a uniform ET protocol, a homogenous uterine environment was created in this carefully selected cohort of women, thereby minimizing confounders and uniquely highlighting the neutral effect of overweight BMI on implantation rate.

Obstetrical and perinatal morbidity and mortality among in-vitro fertilization pregnancies: a population-based study

PURPOSE

To compare patient characteristics and obstetrical/neonatal outcomes of in-vitro fertilization (IVF) and spontaneously conceived pregnancies.

METHODS

Using the Nationwide Inpatient Sample, we conducted a retrospective cohort study from 2008 to 2011 comparing IVF conceptions to spontaneous ones. Patient characteristics were descriptively compared, and after adjusting for baseline characteristics with logistic regression, obstetrical/neonatal outcomes were also compared.

RESULTS

Among 3,315,764 pregnancies, 5773 (0.17%) were a result of IVF. These patients were more often older, wealthier, Caucasian, non-smokers, and more likely to carry a higher order pregnancy. IVF was strongly associated with pre-eclampsia (OR 1.48, 95% CI 1.32-1.62), gestational diabetes (OR 1.27, 95% CI 1.17-1.38), antepartum hemorrhage (OR 2.04, 95% CI 1.79-2.32), placenta previa (OR 3.14, 95% CI 2.71-3.64), pre-term premature rupture of membranes (OR 1.49, 95% CI 1.30-1.70), chorioamnionitis (OR 1.52, 1.29-1.79), and cesarean section (OR 1.60, 95% CI 1.51-1.70). There was a significantly increased risk of post-partum hemorrhage (OR 2.95, 95% CI 2.29-3.80) and hysterectomy (OR 1.73, 95% CI 1.12-2.69), as well as disseminated intravascular coagulopathy (OR 2.23, 95% CI 1.24-3.99), transfusion (OR 1.78, 95% CI 1.53-2.07), prolonged hospitalization (OR 1.96, 95% CI 1.80-2.14), intrauterine growth restriction (OR 1.81, 95% CI 1.63-2.02), and pre-term birth (OR 1.31, 95% CI 1.22-1.41).

CONCLUSION

IVF is still primarily used by only a subset of the population, and is associated with increased obstetrical and perinatal morbidity and mortality. These patients may benefit from more vigilant antenatal surveillance and delivery in a tertiary care center.

High oestradiol concentration after ovarian stimulation is associated with lower maternal serum beta-HCG concentration and neonatal birth weight

In this retrospective study, the relationship between maternal serum oestradiol and progesterone levels after fresh embryo transfer or frozen embryo transfer (FET), and serum beta-HCG levels in early pregnancy and neonatal birth weight was examined. Included for analysis were 5643 conceived singletons: 2610 after FET and 3033 after fresh embryo transfer. Outcome measures included maternal serum oestradiol, progesterone, beta-HCG levels during the peri-implantation period, birth weight and small-for-gestational-age (SGA). Results at 4, 5 and 6 weeks' gestation were as follows: serum oestradiol and progesterone levels were significantly higher in women who underwent fresh embryo transfer compared with FET (all P < 0.0001 except progesterone at 6 weeks; P = 0.009); for fresh embryo transfers, serum beta-HCG levels were significantly lower than in women who underwent FET (P < 0.0001); beta-HCG levels were negatively correlated with serum oestradiol; and birth weight was negatively correlated with serum oestradiol. Incidence of SGA in fresh embryo transfer was increased significantly compared with FET (P < 0.001). Higher maternal oestradiol levels after fresh embryo transfer was correlated with lower beta-HCG in early pregnancy, lower birth weight and higher incidence of SGA.

Vitrified-warmed single-embryo transfers may be associated with increased maternal complications compared with fresh single-embryo transfers

Cryopreservation of embryos allows single-embryo transfer and storage of supernumerary embryos, maximizing cumulative pregnancy rates. The purpose of this retrospective cohort study was to compare pregnancy outcome in singletons born after fresh or vitrified-warmed single blastocyst transfer (SBT). Singleton live births resulting from SBT of fresh or vitrified-warmed embryos were compared. Primary outcomes were perinatal outcomes including small for gestational age (SGA), low birthweight, preterm deliveries (PTD), large for gestational age (LGA) and congenital malformations. Maternal complications included pre-eclampsia, placenta previa, placental abruption, gestational diabetes mellitus (GDM) and chorioamnionitis. Adjustment for confounding factors was performed. Of 1886 fresh SBTs and 1200 vitrified-warmed SBTs during the study period, vitrified-warmed SBTs compared with fresh SBTs resulted in significantly lower clinical pregnancy rate (P < 0.0001). Live birth and miscarriage rates calculated only for pregnancy with known outcome revealed lower live birth rates and higher miscarriage rates for the vitrified-warmed group. Perinatal complications were calculated for clinical pregnancies with known outcomes (12.9% catchment failure was excluded from analysis). The vitrified-warmed group showed a trend toward higher rates of pre-eclampsia, GDM, Caesarean delivery and LGA neonates. Rates of PTD and SGA were comparable. In conclusion, vitrified-warmed SBT might be associated with increased feto-maternal complications.

Assisted reproduction technique outcomes for fresh versus deferred cryopreserved day-2 embryo transfer: a retrospective matched cohort study

Ovarian stimulation could adversely affect endometrial receptivity and consequently embryo implantation. One emerging strategy is the 'freeze-all' approach. Most studies have focused on blastocyst transfers, with limited research on day-2 deferred cryopreserved embryo transfers. In this large retrospective cohort study, outcomes were compared between day-2 fresh versus deferred cryopreserved embryo transfers. After matching by age and number of previous cycles, 325 cycles were included in the fresh group and 325 in the deferred cryopreserved embryo transfers group: no significant differences were found between groups in implantation (0.20 ± 0.33 versus 0.17 ± 0.31, respectively) and ongoing pregnancy rates (21.85% versus 18.46%). Independent predictors for ongoing pregnancy after a multiple logistic regression analysis were the women's age (OR = 0.92; 95% CI 0.88 to 0.97), body mass index (OR = 0.94; 95% CI 0.89 to 0.99), the number of two pronuclei embryos (OR = 1.19; 95% CI 1.04 to 1.40) and at least one grade 1 embryo transferred (OR = 1.97; 95% CI 1.26 to 3.05). In the case of a day-2 embryo transfer, outcomes after treatment with assisted reproduction techniques are similar for fresh versus deferred cryopreserved embryo transfers when pre-transfer progesterone exposures are similar in the two groups.

Optimal embryo transfer strategy in poor response may include freeze-all

PURPOSE

In this retrospective cohort study, we investigated the best embryo transfer strategy in ICSI cycles with ≤4 oocytes collected at oocyte retrieval.

METHODS

Women who underwent antagonist co-treatment COS for ICSI treatment between January 2010 and December 2015 at a private ART clinic (N = 2263). Eight hundred seventy-nine women (group 1) had ≤4 oocytes collected at oocyte retrieval, of whom 645 (group A) had cleavage stage embryo transfer (ET), and 234 (group B) had blastocyst ET. One thousand three hundred eighty-four women (group 2) had 10-15 oocytes collected at oocyte retrieval, of whom 676 (group C) had cleavage stage ET, and 708 women (group D) had blastocyst ET. Blastocyst vitrification was performed using the Cryotop method and FET using artificial cycles.

RESULTS

In group 1, the cancellation rate was significantly lower in group A (25.2 vs 38 %). The pregnancy rate (PR), clinical PR, implantation rate (IR), and live birth rate (LBR) per ET and per oocyte retrieval were all lower in group A. The clinical PR, IR, and LBR per ET of vitrified-warmed blastocyst ET were significantly the highest. In group 2, the cycle cancellation rate was significantly lower in group C (3.5 vs 13.4 %). The PR, clinical PR, and IR per ET and per oocyte retrieval were all lower in group C. The LBR per ET was significantly lower, but the LBR per oocyte retrieval was not significantly lower in group C. Again, the PR, clinical PR, and IR per ET of vitrified-warmed blastocyst ET were significantly the highest.

CONCLUSIONS

Day 5 ET strategy has been reserved for normal or high responders. The improved pregnancy outcomes from blastocyst culture and cryopreservation may challenge ART to extend this benefit to poor responders.

Risk of adverse pregnancy and perinatal outcomes after high technology infertility treatment: a comprehensive systematic review

In the literature, there is growing evidence that subfertile patients who conceived after infertility treatments have an increased risk of pregnancy and perinatal complications and this is particularly true for patients who conceived through use of high technology infertility treatments. Moreover, high technology infertility treatments include many concomitant clinical and biological risk factors. This review aims to summarize in a systematic fashion the current evidence regarding the relative effect of the different procedures for high technology infertility treatments on the risk of adverse pregnancy and perinatal outcome. A literature search up to August 2016 was performed in IBSS, SocINDEX, Institute for Scientific Information, PubMed, Web of Science and Google Scholar and an evidence-based hierarchy was used to determine which articles to include and analyze. Data on prepregnancy maternal factors, low technology interventions, specific procedures for male factor, ovarian tissue/ovary and uterus transplantation, and chromosomal abnormalities and malformations of the offspring were excluded. The available evidences were analyzed assessing the level and the quality of evidence according to the Oxford Centre for Evidence-Based Medicine guidelines and the Grading of Recommendations Assessment, Development, and Evaluation system, respectively. Current review highlights that every single procedure of high technology infertility treatments can play a crucial role in increasing the risk of pregnancy and perinatal complications. Due to the suboptimal level and quality of the current evidence, further well-designed studies are needed.

Fresh versus frozen: initial transfer or cumulative cycle results: how do we interpret results and design studies?

The way we practice assisted reproductive technology has changed over time. In many ways these changes have been positive as technology has improved, in vitro culture has improved, and embryo selection increasingly allows a single embryo transfer with high success rates and ever smaller multiple birth rates. However, our specialty has often been criticized for not being critical with respect to the acceptance of new technology. Although the outcome of interest seems clear (increasing birth of a healthy baby), the approach can be more complicated; and as there is a de-linking of egg retrieval and ET, and as costs and procedures increase, we should be rigorous about our acceptance of change. This is not to stall change but to encourage the same rigor and questioning of accepted dogma expected in other fields of medicine. An approach based on standard clinical study design to allow appropriate comparisons between patients, and to allow the most comprehensive information for patient counseling, is presented.

Peri-Implantation Hormonal Milieu: Elucidating Mechanisms of Adverse Neurodevelopmental Outcomes

While live births resulting from assisted reproductive technology (ART) exceed 1% of total births annually, the effect of ART on fetal development is not well understood. Data have demonstrated that IVF leads to alterations in DNA methylation and gene expression in the placenta that may have long-term effects on health and disease. Studies have linked adverse neurodevelopmental outcomes to ART, although human studies are inconclusive. In order to isolate the peri-implantation environment and its effects on brain development, we utilized a mouse model with and without superovulation and examined the effect of adult behavior as well as adult cortical neuronal density. Adult offspring of superovulated dams showed increased anxiety-like behavior compared to offspring of naturally mated dams (P < .05). There was no difference in memory and learning tests between the 2 groups. The adult brains from offspring of superovulated recipients had fewer neurons per field compared to naturally mated control offspring (P < .05). In order to examine potential pathways leading to these changes, we measured messenger RNA and microRNA (miRNA) expression in fetal brains at E18.5. Microarray analysis found that miRNAs miR-122, miR-144, and miR-211, involved in regulation of neuronal migration and differentiation, were downregulated in brains of offspring exposed to a superovulated environment(P < .05). There was also altered expression of genes involved in neuronal development. These results suggest that the peri-implantation environment can affect neurodevelopment and can lead to behavioral changes in adulthood. Human studies with long-term follow-up of children from ART are necessary to further investigate the influence of ART on the offspring.

Gonadotropin-releasing hormone agonist triggering of oocyte maturation in assisted reproductive technology cycles

Gonadotropin-releasing hormone agonists (GnRHa) have gained increasing attention in the last decade as an alternative trigger for oocyte maturation in patients at high risk for ovarian hyperstimulation syndrome (OHSS). They provide a short luteinizing hormone (LH) peak that limits the production of vascular endothelial growth factor, which is the key mediator leading to increased vascular permeability, the hallmark of OHSS. Initial studies showed similar oocyte yield and embryo quality compared with conventional human chorionic gonadotropin (hCG) triggering; however, lower pregnancy rates and higher miscarriage rates were alarming in GnRHa triggered groups. Therefore, two approaches have been implemented to rescue the luteal phase in fresh transfers. Intensive luteal phase support (iLPS) involves administiration of high doses of progesterone and estrogen and active patient monitoring. iLPS has been shown to provide satisfactory fertilization and clinical pregnancy rates, and to be especially useful in patients with high endogenous LH levels, such as in polycystic ovary syndrome. The other method for luteal phase rescue is low-dose hCG administiration 35 hours after GnRHa trigger. Likewise, this method results in statistically similar ongoing pregnancy rates (although slightly lower than) to those of hCG triggered cycles. GnRHa triggering decreased OHSS rates dramatically, however, none of the rescue methods prevent OHSS totally. Cases were reported even in patients who underwent cryopreservation and did not receive hCG. GnRH triggering induces a follicle stimulating hormone (FSH) surge, similar to natural cycles. Its possible benefits have been investigated and dual triggering, GnRHa trigger accompanied by a simultaneous low-dose hCG injection, has produced promising results that urge further exploration. Last of all, GnRHa triggering is useful in fertility preservation cycles in patients with hormone sensitive tumors. In conclusion, GnRHa triggering accompanied by appropriate luteal phase rescue protocols is a relatively safe option for patients at high risk for OHSS.

Outcome Analysis of Day-3 Frozen Embryo Transfer v/s Fresh Embryo Transfer in Infertility: A Prospective Therapeutic Study in Indian Scenario

INTRODUCTION

Advanced fertilization techniques like frozen embryo transfer (FET) and assisted reproductive technology have become popular and commonly used methods to treat patients suffering from infertility. Incidences of infertility are on a rise due to increased representation of females in the work place, delay in marriages, stress, and ignorance.

METHODS

We performed this prospective therapeutic study to compare FET and fresh embryo transfer in the treatment of infertility in terms of conception rate, patient acceptance, complications, and patient's compliance. A prospective screening therapeutic study on 108 patients, from September 2013 to September 2014 in Karnataka, India, randomized the patients into 2 groups (n = 54), Group-I treated with day-3 FET while Group-II was treated with fresh embryo transfer, after performing ICSI.

RESULTS

In 108 patients, 45 % patients were within 35 years of age, 35 % were in the age group 35-39. Significantly, 22 (40.75 %) patients treated with FET conceived (P = 0.022), whereas 16 (29.63 %) patients treated with fresh embryo transfer conceived (P = 0.59).

DISCUSSION

There is limited published literature from the subcontinent, comparing techniques like FET and embryo transfers in the treatment of infertility. Awareness and economic reforms must be formulated in India to facilitate individuals facing infertility problems to conceive.

CONCLUSION

FET has better and significant conception rates compared to fresh embryo transfers. FET shares an advantage of providing good quality embryos for future and subsequent implantations in cases of failure. Patient counseling and motivation play a pivotal role in the success of therapeutic procedure.

GnRH agonist triggers and their use in assisted reproductive technology: the past, the present and the future

Gonadotropin releasing hormone agonist triggers are very effective in eliminating early-onset ovarian hyperstimulation syndrome (OHSS). However, in most studies they result in inferior pregnancy rates compared to hCG triggers in fresh autologous transfers. This is not due to an effect on embryo quality but rather due to inadequate corpus luteum formation and a defective luteal phase causing poor implantation. Intensive and adjusted steroid support or low-dose hCG may correct this. Late-onset OHSS is eliminated by using a freeze-all strategy. Pregnancy rates after transfer of thawed vitrified embryos are consistently high. A strategy combining a gonadotropin releasing hormone agonist trigger with vitrification of all embryos has been proposed as a means of achieving a truly OHSS-free clinic.

Does the type of culture medium used influence birthweight of children born after IVF?

STUDY QUESTION

Do culture media influence birthweight of children born after IVF?

SUMMARY ANSWER

Some studies have observed a significant effect of culture media on birthweight, while others have not, but since most studies compared different culture media, conventional meta-analysis was not possible.

WHAT IS KNOWN ALREADY

Animal studies suggest that in vitro culture of embryos can have a significant effect on the birthweight of offspring when compared with in vivo developed embryos. The type of culture medium (or certain components of the medium) used is one of the causal factors.

STUDY DESIGN, SIZE, DURATION

We reviewed all available literature reporting on a relation between culture medium and birthweight in human studies and a selection of animal studies.

PARTICIPANTS/MATERIALS, SETTING, METHODS

An extensive literature search on Pubmed and Medline was performed with relevant search criteria relating to IVF, birthweight and culture medium.

MAIN RESULTS AND THE ROLE OF CHANCE

Eleven studies reporting on a relationship between culture medium and birthweight in human were included in this review. Five of these found significant differences in birthweight when offspring born after culture in different culture media were compared. The remaining studies did not find differences in birthweight after changing culture medium.

LIMITATIONS, REASONS FOR CAUTION

The number of human studies is limited and different culture media with different compositions are compared which makes a comparison between the studies difficult, if not impossible. Furthermore, most study designs were retrospective with consecutive use of different culture media and limited sample sizes, which makes bias of the results likely.

WIDER IMPLICATIONS OF THE FINDINGS

If it could be confirmed that the type of culture medium used does indeed influence phenotypic characteristics (such as birthweight) of children born after IVF, it would underline the importance of monitoring the health of IVF children in relation to aspects of the laboratory techniques used during embryo culture.

STUDY FUNDING/COMPETING INTERESTS

No funding was applicable to this study. No conflict of interest is declared.

Fresh versus frozen embryo transfer: backing clinical decisions with scientific and clinical evidence

BACKGROUND

Improvements in vitrification now make frozen embryo transfers (FETs) a viable alternative to fresh embryo transfer, with reports from observational studies and randomized controlled trials suggesting that: (i) the endometrium in stimulated cycles is not optimally prepared for implantation; (ii) pregnancy rates are increased following FET and (iii) perinatal outcomes are less affected after FET.

METHODS

This review integrates and discusses the available clinical and scientific evidence supporting embryo transfer in a natural cycle.

RESULTS

Laboratory-based studies demonstrate morphological and molecular changes to the endometrium and reduced responsiveness of the endometrium to hCG, resulting from controlled ovarian stimulation. The literature demonstrates reduced endometrial receptivity in controlled ovarian stimulation cycles and supports the clinical observations that FET reduces the risk of ovarian hyperstimulation syndrome and improves outcomes for both the mother and baby.

CONCLUSIONS

This review provides the basis for an evidence-based approach towards changes in routine IVF, which may ultimately result in higher delivery rates of healthier term babies.

Why we should transfer frozen instead of fresh embryos: the translational rationale

Epidemiologic studies have shown an increased rate of adverse perinatal outcomes, including small for gestational age (SGA) births, in fresh in vitro fertilization (IVF) cycles compared with frozen embryo transfer cycles. This increase is not seen in the donor oocyte population, suggesting that it is the peri-implantation environment created after superovulation that is responsible for these changes. During a fresh IVF cycle, multiple corpora lutea secrete high levels of hormones and other factors that can affect the endometrium and the implanting embryo. In this review, we discuss both animal and human data demonstrating that superovulation has significant effects on the endometrium and embryo. Additionally, potential mechanisms for the adverse effects of gonadotropin stimulation on implantation and placental development are proposed. We think that these data, along with the growing body of epidemiologic evidence, support the proposal that frozen embryo transfer should be considered preferentially, particularly in high responders, as a means to potentially decrease at least some of the adverse perinatal outcomes associated with IVF.

Clinical rationale for cryopreservation of entire embryo cohorts in lieu of fresh transfer

Recent dramatic increases in success rates with frozen-thawed embryo transfer (FET) are encouraging, as are numerous findings of several reduced risks with FET when compared with fresh transfer. These reduced risks include low birth weight and prematurity, among others. However, FET is also associated with increased risks of macrosomia and large for gestational age. There have been reports of greater implantation and pregnancy rates with FET than with fresh autologous embryo transfer, suggesting superior endometrial receptivity in the absence of ovarian stimulation. As cryo-technology evolves, there is potential for further increase in FET success rates, but for now it may be best to follow an individualized approach, balancing fresh transfer and embryo cohort cryopreservation options while considering patient characteristics, cycle parameters, and clinic success rates.

Live birth after fresh embryo transfer vs elective embryo cryopreservation/frozen embryo transfer in women with polycystic ovary syndrome undergoing IVF (FreFro-PCOS): study protocol for a multicenter, prospective, randomized controlled clinical trial

Background

Polycystic ovary syndrome (PCOS) patients are at increased risk of pregnancy complications, which may impair pregnancy outcome. Transfer of fresh embryos after superovulation may lead to abnormal implantation and placentation and further increase risk for pregnancy loss and complications. Some preliminary data suggest that elective embryo cryopreservation followed by frozen–thawed embryo transfer into a hormonally primed endometrium could result in a higher clinical pregnancy rate than that achieved by fresh embryo transfer.

Methods/Design

This study is a multicenter, prospective, randomized controlled clinical trial (1:1 treatment ratio of fresh vs. elective frozen embryo transfers).. A total of 1,180 infertile PCOS patients undergoing the first cycle of in vitro fertilization (IVF) or intracytoplasmic sperm injection will be enrolled and randomized into two parallel groups. Participants in group A will undergo fresh embryo transfer on day 3 after oocyte retrieval, and participants in group B will undergo elective embryo cryopreservation after oocyte retrieval and frozen–thawed embryo transfer in programmed cycles. The primary outcome is the live birth rate. Our study is powered at 80 to detect an absolute difference of 10 at the significance level of 0.01 based on a two-sided test.

Discussion

We hypothesize that elective embryo cryopreservation and frozen–thawed embryo transfer will reduce the incidence of pregnancy complications and increase the live birth rate in PCOS patients who need IVF to achieve pregnancy.

Trial registration

ClinicalTrials.gov Identifier: NCT01841528