Are perinatal outcomes affected by blastocyst vitrification and warming?

Vitrification of human blastocysts for couples undergoing assisted reproduction: an updated review

Over the past 40 years there has been a worldwide critical change in the field of assisted reproduction technology (ART), leading to the increased application of single blastocyst transfer, which is extremely important to avoid the risks of multiple pregnancy and associated complications for both mother and babies. Indeed, advancements in ART over the last few decades have been obtained thanks to several improvements, including ovarian stimulation, embryo culture conditions and, of course, progress in cryopreservation methods, especially with the application of vitrification. The ability to cryopreserve human embryos has improved significantly with vitrification compared to the initially adopted slow-freezing procedures. Since the introduction of vitrification, it has become the gold standard method to effectively cryopreserve human blastocysts. However, some new protocols are now being explored, such as the short warming procedure and even shorter exposure to the equilibration solution before vitrification, which seem to provide optimal results. Therefore, the main aim of the current narrative review, will be to illustrate the benefit of vitrification as an effective method to cryopreserve the human blastocyst and to illustrate new protocols and variations which in future may increase the performance of vitrification protocols.

Review of human oocyte cryopreservation in ART programs: Current challenges and opportunities

Oocyte cryopreservation has notably increased in recent times, to become an essential part of clinical infertility treatment. Since the 1980s, many improvements in oocyte cryopreservation (OC) have been adopted, including the great advance with the application of vitrification. The commonly used vitrification protocol applies different cryoprotectants (Ethylene glycol and/or DMSO and/or PROH and sucrose and/or Trehalose) and two different steps: firstly, exposure in equilibration solution for 5-15 min, followed by a vitrification solution for 60-90 s at room temperature. The warming method includes a first step for 1 min at 37 °C and 3 subsequent steps at room temperature to remove the cryoprotectant for a total of 9-12 min. In addition, biosafety is a critical aspect to mention, and it is related to devices used during the vitrification, mainly in terms of whether the biological vitrified material comes in direct contact with liquid nitrogen (open vitrification) or not (closed vitrification), where LN2 may contain potentially contaminating viruses or pathogens. Furthermore, during early development major waves of epigenetic reprogramming take place. Recent literature suggests that epigenetic and transcriptomic profiles are sensitive to the stress induced by vitrification, including osmotic shock, temperature, rapid changes of pH and toxicity of cryoprotectants. It is, therefore, important to better understand the potential perturbations of epigenetic modifications that may be associated with the globally used vitrification methods. Therefore, we here discuss the benefits and efficiency of human oocyte vitrification; we also review the evidence surrounding oocyte cryopreservation-related epigenetic modifications and potential epigenetic dysregulations, together with long-term consequences for offspring health.

Increased Risk of Preeclampsia with Assisted Reproductive Technologies

PURPOSE OF REVIEW

We summarized recent available data to assess the association between assisted reproductive technology (ART) and risk for preeclampsia.

RECENT FINDINGS

The majority of clinical studies supporting the association of preeclampsia and ART are retrospective. Published data from both clinical and pre-clinical studies suggest specific ART procedures may contribute to the increased risk, including in vitro embryo handling and development, hormone stimulation, transfer cycle types, and use of donor oocytes/embryos. Potential mechanisms include epigenetic aberrations leading to abnormal placentation, absence of factors secreted by the corpus luteum, and immunologic responses to allogenic gametes. There is an increased risk of preeclampsia following ART. Treatment plans that favor reduced preeclampsia risk should be considered for ART pregnancies. To make ART pregnancies safer, additional clinical and animal model studies are needed to elucidate the underpinnings of this risk association.

Is artificial endometrial preparation more associated with early-onset or late-onset preeclampsia after frozen embryo transfer?

PURPOSE

To explore whether the risks of early- or late-onset preeclampsia vary among frozen embryo transfer (FET) with different regimens for endometrial preparation and fresh embryo transfer (FreET).

METHODS

We retrospectively included a total of 24129 women who achieved singleton delivery during their first cycles of in vitro fertilization (IVF) between January 2012 and March 2020. The risks of early- and late-onset preeclampsia after FET with endometrial preparation by natural ovulation cycles (FET-NC) or by artificial cycles (FET-AC) were compared to that after FreET.

RESULTS

After adjustment via multivariable logistic regression, the total risk of preeclampsia was higher in the FET-AC group compared to the FreET group [2.2% vs. 0.9%; adjusted odds ratio (aOR): 2.00; 95% confidence interval (CI): 1.45-2.76] and FET-NC group (2.2% vs. 0.9%; aOR: 2.17; 95% CI: 1.59-2.96).When stratified by the gestational age at delivery based on < 34 weeks or ≥ 34 weeks, the risk of late-onset preeclampsia remained higher in the FET-AC group than that in the and FreET group (1.8% vs. 0.6%; aOR: 2.56; 95% CI: 1.83-3.58) and the FET-NC group (1.8% vs. 0.6%; aOR: 2.63; 95% CI: 1.86-3.73). We did not find a statistically significant difference in the risk of early-onset preeclampsia among the three groups.

CONCLUSIONS

An artificial regimen for endometrial preparation was more associated with an increased risk of late-onset preeclampsia after FET. Given that FET-AC is widely used in clinical practice, the potential maternal risk factors for late-onset preeclampsia when using the FET-AC regimen should be further explored, considering the maternal origin of late-onset preeclampsia.

Effects of Rederivation by Embryo Vitrification on Performance in a Rabbit Paternal Line

Embryo cryopreservation is a valuable tool for maintaining genetic variability and preserving breeds and lines, allowing to assess the response to selection and enabling genetic diffusion. This study aimed to evaluate the impact of rederivation by embryo vitrification and transfer procedures on the growth and reproductive traits in a paternal rabbit line selected for average daily gain from weaning (28 days old) to fattening (63 days old). The rederived population was bred over two generations at the same time as a control population of this paternal line and, growth trait parameters (weights at weaning, end of the fattening period, and average daily gain) and reproductive performance (kindling rate, litter size at birth and at weaning) were compared with three filial generations. Moreover, fetal growth and litter size components were assessed for the second generation by ultrasonography and laparoscopy. Differences in postnatal growth traits (end of fattening weight and average daily gain) were observed in the three generations assessed. However, fetal growth, litter size components, and reproductive traits did not show significant differences. In conclusion, cryopreservation and embryo transfer processes cause changes in growth traits of reconstituted populations that influence the following generations, without changes in reproductive traits in a paternal line of rabbits.

Potential role of the corpus luteum in maternal cardiovascular adaptation to pregnancy and preeclampsia risk

Studies in the gravid rat model revealed a key role for the corpus luteal hormone, relaxin, in the maternal circulatory changes of early pregnancy epitomized by profound systemic vasodilation and increased arterial compliance. To determine whether the corpus luteum may play a similar role in human pregnancy, women who conceived by in vitro fertilization were studied. Implementation of artificial (programmed) cycles for embryo transfers, which precluded the formation of a corpus luteum, was associated with notable attenuation of the gestational rise in cardiac output and fall in carotid-femoral pulse wave velocity (reflecting impairment of arterial dilation and increased compliance, respectively) and deficiencies in other cardiovascular changes normally observed during the first trimester. Cardiac output and carotid-femoral pulse wave velocity were restored after the first trimester of pregnancy, consistent with rescue by placental vasodilators, such as placental growth factor. In addition, a potential role of corpus luteal factors in reducing the risk of developing preeclampsia was hypothesized. In most single and multiple center, prospective and retrospective cohort (and registry) studies, the risk of developing preeclampsia and preeclampsia with severe features was increased specifically in women undergoing autologous frozen embryo transfer in artificial cycles without the formation of a corpus luteum relative to natural, modified natural, stimulated, or controlled ovarian stimulation cycles and spontaneous pregnancies-all associated with the formation of at least 1 corpus luteum. Taken together, these observational studies are sufficiently compelling to warrant randomized clinical trials comparing preeclampsia risk in autologous frozen embryo transfer in natural vs artificial cycles. Impaired endometrial function because of suboptimal hormonal administration is an alternative but not mutually exclusive explanation for increased preeclampsia risk in autologous frozen embryo transfer in artificial cycles. Potential mechanisms by which the corpus luteum may reduce the risk of developing preeclampsia and whether autologous frozen embryo transfer in artificial cycles is associated with increased risk of preterm preeclampsia, term preeclampsia, or both are discussed. Last, suggestions for future investigations are noted.

The vitrification system may affect preterm and cesarean delivery rates after single vitrified blastocyst transfer

The purpose of this study was to investigate the possible effects of different vitrification systems on single vitrified blastocyst transfer cycles. The clinical and birth outcomes of 412 patients who underwent single vitrified blastocyst transfer between January 2018 and June 2020 were retrospectively analyzed and compared between patients who underwent blastocyst vitrification with kit A (group A, 196 patients) and those who underwent blastocyst vitrification with kit B (group B, 216 patients). Clinical outcomes, including the clinical pregnancy rate, ongoing pregnancy rate, early miscarriage rate, late miscarriage rate, ectopic pregnancy rate, twin pregnancy rate, and induced labor rate due to fetal malformation, were not significantly different between the two groups (P > 0.05). The preterm delivery rate among singleton newborns (11.57% vs. 3.23%, P < 0.05) and the cesarean delivery rate were significantly higher in group B than in group A (70.25% vs. 57.26%, P < 0.05). Birth outcomes, including the male-to-female ratio, low-birth-weight rate, macrosomia rate, birth defect rate, newborn gestational age, neonatal body weight, and singleton neonatal body length, were not significantly different (P > 0.05). Our findings suggest that different vitrification systems might differentially affect birth outcomes. Such disparity could reflect differences in kit composition and/or protocol.ABBREVIATIONS: DMSO: dimethyl sulfoxide; ES: equilibration solution; VS: vitrification solution; BMI: body mass index; ICSI: intracytoplasmic sperm injection; OR: odds ratio; CI: confidence interval.

Do frozen embryo transfers modify the epigenetic control of imprinted genes and transposable elements in newborns compared with fresh embryo transfers and natural conceptions?

OBJECTIVE

To determine whether the epigenetic control of imprinted genes (IGs) and transposable elements (TEs) differs at birth between fresh or frozen embryo transfers and natural conceptions.

DESIGN

Prospective study.

SETTING

University hospital.

PATIENT(S)

A total of 202 singleton births were divided into three groups: 84 natural pregnancies (controls), 66 in vitro fertilization/intracytoplasmic sperm injection with fresh embryo transfers, and 52 vitro fertilization/intracytoplasmic sperm injection with frozen embryo transfers.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Pyrosequencing was used to assess the DNA methylation profiles of three IGs (H19/IGF2:IG-DMR [two sequences], KCNQ1OT1:TSS-DMR, and SNURF:TSS-DMR) and two TEs (LINE-1 and HERV-FRD) in cord blood and placenta. The quantitative reverse transcriptase polymerase chain reaction was used to study the transcription of three IGs (H19, KCNQ1, and SNRPN) and two TEs (LINE-1 and ORF2).

RESULT(S)

After adjustment, the placental DNA methylation levels of H19/IGF2 were lower in the fresh embryo transfer group than in the control (H19/IGF2-seq1) and frozen embryo transfer (H19/IGF2-seq2) groups. The DNA methylation rate for LINE-1 was lower in placentas from the fresh embryo transfer group than in placentas from the control and frozen embryo transfer groups and for HERV-FRD compared with controls. In cord blood, DNA methylation levels were not significantly associated with the mode of conception. The relative expression of LINE-1 and ORF2 was decreased in both cord blood and placental tissues from fresh embryo transfer conceptions compared with natural conceptions and frozen embryo transfer conceptions.

CONCLUSION(S)

Compared with natural conceptions and frozen embryo transfers, fresh embryo transfers were associated with methylation and/or transcription changes in some TEs and IGs, mostly in placental samples, which could indicate altered placental epigenetic regulation resulting from ovarian stimulation protocols.

Embryo biopsy and maternal and neonatal outcomes following cryopreserved-thawed single embryo transfer

BACKGROUND

Contemporary embryo biopsy in the United States involves the removal of several cells from a blastocyst that would become the placenta for preimplantation genetic testing. Embryos are then cryopreserved while patients await biopsy results, with transfers occurring in a subsequent cycle as a single frozen-thawed embryo transfer, if euploid.

OBJECTIVE

We sought to determine if removal of these cells for preimplantation genetic testing was associated with adverse obstetrical or neonatal outcomes after frozen-thawed single embryo transfer.

STUDY DESIGN

We linked assisted reproductive technology surveillance data from the Society for Assisted Reproductive Technology Clinic Outcome Reporting System to birth certificates and maternal and neonatal hospitalization discharge diagnoses in Massachusetts from 2014 to 2017, considering only singleton births after frozen-thawed single embryo transfers. We compared outcomes of cycles having embryo biopsy (n=585) to those having no biopsy (n=2191) using chi-square for categorical and binary variables and logistic regression for adjusted odds ratios and 95% confidence intervals, adjusting for mother's age, race, education, parity, body mass index, birth year, insurance, and all infertility diagnoses.

RESULTS

Considering no biopsy as the reference, there was no difference between groups with respect to preeclampsia (adjusted odds ratio, 0.82; 95% confidence interval, 0.42-1.61; P=.5685); pregnancy-induced hypertension (adjusted odds ratio, 0.85; 95% confidence interval, 0.46-1.59; P=.6146); placental disorders, including placental abruption, placenta previa, placenta accreta, placenta increta, and placenta percreta (adjusted odds ratio, 1.16; 95% confidence interval, 0.60-2.24; P=.6675); preterm birth (adjusted odds ratio, 1.22; 95% confidence interval 0.73-2.03; P=.4418); low birthweight (adjusted odds ratio, 1.12; 95% confidence interval, 0.58-2.15; P=.7355); cesarean delivery (adjusted odds ratio, 1.04; 95% confidence interval, 0.79-1.38; P=.7762); or gestational diabetes mellitus (adjusted odds ratio, 0.83; 95% confidence interval, 0.50-1.38; P=.4734). In addition, there was no difference between the groups for prolonged hospital stay for mothers (adjusted odds ratio, 1.23; 95% confidence interval, 0.83-1.80; P=.3014) or for infants (95% confidence interval, 1.29; 95% confidence interval, 0.72-2.29; P=.3923).

CONCLUSION

Embryo biopsy for preimplantation genetic testing does not increase the odds for diagnoses related to placentation (preeclampsia, pregnancy-related hypertension, placental disorders, preterm delivery, or low birthweight), maternal conditions (gestational diabetes mellitus), or maternal or infant length of stay after delivery.

Higher estradiol levels are associated with lower neonatal birthweight after fresh and frozen embryo transfers. A cohort study of 3631 singleton IVF pregnancies

AIM

To assess the birthweight of neonates conceived after fresh and frozen embryo transfers (FET) and, if different, to investigate whether estradiol levels during the late follicular phase were associated with the observed difference.

METHODS

Singleton pregnancies from fresh and FET transfers between January 1990 and December 2013 were compared retrospectively. A total of 2885 singleton pregnancies after fresh embryo transfer and 746 after FET were analyzed. Obstetric and neonatal outcomes were compared between fresh and FET cycles.

RESULTS

The singletons born after FET were found to have a significantly higher birth weight (3313 g), compared to those born after fresh embryo transfer (3143 g); p < .001. The main predictor of this difference was found to be estradiol levels at the end of the follicular phase. The difference in birthweight was inversely correlated to estradiol levels considering all cycles together but also considering fresh and frozen cycles separately.

CONCLUSIONS

Our study demonstrates a link between high estradiol levels and low birth weight of singletons after IVF both in fresh and frozen-thawed embryo transfer cycles. It provides additional support to the involvement of hyperestrogenemia in the process of implantation and on the subsequent fetal development.

Secretory products of the corpus luteum and preeclampsia

BACKGROUND

Despite significant advances in our understanding of the pathophysiology of preeclampsia (PE), there are still many unknowns and controversies in the field. Women undergoing frozen-thawed embryo transfer (FET) to a hormonally prepared endometrium have been found to have an unexpected increased risk of PE compared to women who receive embryos in a natural FET cycle. The differences in risk have been hypothesized to be related to the absence or presence of a functioning corpus luteum (CL).

OBJECTIVE AND RATIONALE

To evaluate the literature on secretory products of the CL that could be essential for a healthy pregnancy and could reduce the risk of PE in the setting of FET.

SEARCH METHODS

For this review, pertinent studies were searched in PubMed/Medline (updated June 2020) using common keywords applied in the field of assisted reproductive technologies, CL physiology and preeclampsia. We also screened the complete list of references in recent publications in English (both animal and human studies) on the topics investigated. Given the design of this work as a narrative review, no formal criteria for study selection or appraisal were utilized.

OUTCOMES

The CL is a major source of multiple factors regulating reproduction. Progesterone, estradiol, relaxin and vasoactive and angiogenic substances produced by the CL have important roles in regulating its functional lifespan and are also secreted into the circulation to act remotely during early stages of pregnancy. Beyond the known actions of progesterone and estradiol on the uterus in early pregnancy, their metabolites have angiogenic properties that may optimize implantation and placentation. Serum levels of relaxin are almost undetectable in pregnant women without a CL, which precludes some maternal cardiovascular and renal adaptations to early pregnancy. We suggest that an imbalance in steroid hormones and their metabolites and polypeptides influencing early physiologic processes such as decidualization, implantation, angiogenesis and maternal haemodynamics could contribute to the increased PE risk among women undergoing programmed FET cycles.

WIDER IMPLICATIONS

A better understanding of the critical roles of the secretory products of the CL during early pregnancy holds the promise of improving the efficacy and safety of ART based on programmed FET cycles.

Frozen Embryo Transfer and Preeclampsia Risk

Worldwide, the use of Assisted Reproductive Technology (ART) has been steadily rising over recent years. With the continuous improvements in cryopreservation techniques and the growing practice of single embryo transfer, the proportion of frozen embryo transfer (FET) cycles has been increasing, therefore raising concern about the safety of this ART technique to both mothers and infants. This review aims to summarize the current evidence regarding the risk of preeclampsia in singleton pregnancies achieved by autologous FET compared to fresh embryo transfer, and to discuss the influence of different protocols used for endometrium preparation in frozen cycles on the risk of this obstetric complication. Several studies have reported a higher risk of hypertensive disorders, including preeclampsia, in pregnancies following FET compared with fresh embryo transfer. Recently, artificial FET cycles, which preclude the development of a corpus luteum, were shown to be associated with an increased preeclampsia risk in comparison with natural and stimulated cycles. Importantly, no difference was found between FET in a modified natural cycle and spontaneous conception. It has been proposed that the absence of the corpus luteum in artificial cycles may, at least partly, contribute to the observed increased risk of preeclampsia. Indeed, the corpus luteum secretes vasoactive hormones, such as relaxin, which are not replaced in artificial cycles, thereby compromising maternal cardiovascular adaptations to pregnancy, resulting in an increased risk of preeclampsia. If these findings are confirmed by a randomized controlled trial, natural, modified natural or stimulated cycles might be preferred over artificial cycles in eligible patients.

Antioxidants increase blastocyst cryosurvival and viability post-vitrification

STUDY QUESTION

What is the effect of antioxidants acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid (A3) in vitrification and warming solutions on mouse blastocyst development and viability?

SUMMARY ANSWER

The combination of three antioxidants in vitrification solutions resulted in mouse blastocysts with higher developmental potential in vitro and increased viability as assessed by both an outgrowth model in vitro and fetal development following uterine transfer.

WHAT IS KNOWN ALREADY

The antioxidant combination of acetyl-L-carnitine, N-acetyl-L-cysteine and α-lipoic acid present in IVF handling and embryo culture media has significant beneficial effects on mouse embryo and fetal development, especially under oxidative stress.

STUDY DESIGN, SIZE, DURATION

The study was a laboratory-based analysis of an animal model. Rapid cooling through vitrification was conducted on F1 mouse blastocysts, with antioxidants (A3) supplemented in vitrification and/or warming solutions, followed by culture and embryo transfer.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

Pronucleate oocytes were collected and cultured in groups to Day 4 blastocysts. Expanded blastocysts were vitrified and warmed in solutions with and without the A3 antioxidants and cultured for a further 24 h. Blastocyst cell number and allocation, apoptosis and histone acetylation levels were all quantified, and viability through outgrowths and transfers assessed.

MAIN RESULTS AND THE ROLE OF CHANCE

Mouse blastocysts vitrified with no antioxidants had significantly lower cell numbers (P  < 0.001) and higher apoptotic cells (P  < 0.05) compared to non-vitrified embryos. Addition of combined A3 antioxidants to the vitrification and warming solutions resulted in a significant increase in inner cell mass cell (ICM) number (P  < 0.001) and total cell number (P  < 0.01), and an increase in outgrowth area (P < 0.05), which correlated with the increased fetal weight (P < 0.05), crown rump length (P < 0.05) and limb development (P < 0.05) determined following transfer compared to embryos with no antioxidants. Furthermore, while blastocyst vitrification significantly reduced acetylation levels (P < 0.05) compared to non-vitrified embryos, the inclusion of A3 antioxidants helped to ameliorate this.

LIMITATIONS, REASONS FOR CAUTION

Embryo development was only examined in the mouse.

WIDER IMPLICATIONS OF THE FINDINGS

Results in this study demonstrate that vitrification and warming of blastocysts have significant detrimental effects on embryo histone acetylation and subsequent viability. The presence of antioxidants in the vitrification solutions helps to alleviate the negative effects of cryopreservation. Our data indicate that antioxidants need to be present in the medium at the time of exposure to increased oxidative stress associated with vitrification and that prior exposure (i.e. during culture or IVF alone) is insufficient to protect cells against cryo-induced injury. Hence, A3 antioxidants may assist in maintaining the viability of vitrified human embryos in ART through the reduction of oxidative stress.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by a research grant from Vitrolife AB (Sweden). The authors have no conflict of interest to declare.

Influence of Placental Abnormalities and Pregnancy-Induced Hypertension in Prematurity Associated with Various Assisted Reproductive Technology Techniques

OBJECTIVE

Assisted reproductive technology (ART)-treated women exhibit increased risk of premature delivery compared to fertile women. We evaluated whether ART treatment modalities increase prematurity and whether placental abnormalities and pregnancy-induced hypertensive (PIH) disorders mediate these risks.

METHOD(S)

This retrospective study of ART-treated and fertile deliveries (2004-2017) used an ART-cycle database linked to Massachusetts birth certificates and hospital discharges. Outcomes of late preterm birth (LPTB: 34-36 weeks gestation) and early preterm birth (EPTB: <34 weeks gestation) were compared with term deliveries (≥37 weeks gestation) in ART-treated (linked to the ART database) and fertile (no indicators of infertility or ART) deliveries. ART treatments with autologous oocyte, donor oocyte, fresh or frozen embryo transfer (FET), intracytoplasmic sperm injection (ICSI) and no-ICSI were separately compared to the fertile group. Adjusted odds ratios (AOR) were calculated with multivariable logistic regression: placental abnormalities or PIH were quantified in the pathway as mediators.

RESULTS

There were 218,320 deliveries: 204,438 fertile and 13,882 ART-treated. All treatment types increased prematurity (AOR 1.31-1.58, LPTB; AOR 1.34-1.48, EPTB). Placental abnormalities mediated in approximately 22% and 38% of the association with LPTB and EPTB, respectively. PIH mediated 25% and 33% of the association with LPTB and EPTB in FET and donor oocyte cycles, more than other treatments (<10% LPTB and <13% EPTB).

CONCLUSIONS

ART-treatment and all ART modalities increased LPTB and EPTB when compared with fertile deliveries. Placental abnormalities modestly mediated associations approximately equally, while PIH was a stronger mediator in FET and donor oocyte cycles. Reasons for differences require exploration.

Health of 2-year-old children born after vitrified oocyte donation in comparison with peers born after fresh oocyte donation

STUDY QUESTION

Does oocyte vitrification adversely affect the health of 2-year-old children compared with peers born after use of fresh oocytes in a donation programme?

SUMMARY ANSWER

The growth and health of 2-year-old children born after oocyte vitrification are similar to those of peers born after use of fresh oocytes.

WHAT IS KNOWN ALREADY

Although oocyte vitrification is a well-established procedure in ART, the evidence on its safety for offspring is limited. Currently, no disadvantageous effects of oocyte vitrification have been shown in terms of obstetric and neonatal outcome. However, no data beyond the neonatal period are available to date.

STUDY DESIGN, SIZE, DURATION

A combined retrospective and prospective observational study was performed in a tertiary reproductive centre. The retrospective data were available in our extensive database of children born after ART. Donor cycles with an oocyte retrieval between January 2010 and March 2017 and a fresh embryo transfer resulting in the livebirth of a singleton were selected from the established oocyte donation programme. Fresh or vitrified oocytes were used in the donor cycles and all pregnancies in oocyte recipients were achieved after ICSI. Only children residing in Belgium were eligible for follow-up.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Biometric and health parameters of 72 children born after oocyte vitrification were compared with those of 41 children born after use of a fresh oocyte. Data were collected by means of questionnaires and physical examinations at the age of 21–30 months. The primary outcome measures were anthropometry and health at 2 years of age.

MAIN RESULTS AND THE ROLE OF CHANCE

Length, weight, BMI, head circumference, left arm circumference and waist circumference at the age of 2 years were comparable between the vitrification and fresh group, also after adjustment for treatment, and maternal and neonatal characteristics (all P > 0.05). Health of the children in terms of hospital admission and surgical intervention rates were comparable between the vitrification and fresh group (both P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

Although the current study is the largest series describing health parameters beyond the neonatal period, the small numbers still preclude definite conclusions.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides the first evidence indicating that oocyte vitrification does not adversely affect the growth and health of offspring beyond the neonatal period.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by Methusalem grants and by grants from Wetenschappelijk Fonds Willy Gepts, all issued by the Vrije Universiteit Brussel. All co-authors declared no conflict of interest in relation to this work. Both the Centre for Reproductive Medicine and the Centre for Medical Genetics from the UZ Brussel have received several educational grants from IBSA, Ferring, MSD and Merck for either research on oocyte vitrification or for establishing the database for follow-up research and organizing the data collection.

Sperm DNA methylation mediates the association of male age on reproductive outcomes among couples undergoing infertility treatment

Parental age at time of offspring conception is increasing in developed countries. Advanced male age is associated with decreased reproductive success and increased risk of adverse neurodevelopmental outcomes in offspring. Mechanisms for these male age effects remain unclear, but changes in sperm DNA methylation over time is one potential explanation. We assessed genome-wide methylation of sperm DNA from 47 semen samples collected from male participants of couples seeking infertility treatment. We report that higher male age was associated with lower likelihood of fertilization and live birth, and poor embryo development (p < 0.05). Furthermore, our multivariable linear models showed male age was associated with alterations in sperm methylation at 1698 CpGs and 1146 regions (q < 0.05), which were associated with > 750 genes enriched in embryonic development, behavior and neurodevelopment among others. High dimensional mediation analyses identified four genes (DEFB126, TPI1P3, PLCH2 and DLGAP2) with age-related sperm differential methylation that accounted for 64% (95% CI 0.42-0.86%; p < 0.05) of the effect of male age on lower fertilization rate. Our findings from this modest IVF population provide evidence for sperm methylation as a mechanism of age-induced poor reproductive outcomes and identifies possible candidate genes for mediating these effects.

Endometrium preparation and perinatal outcomes in women undergoing single-blastocyst transfer in frozen cycles

OBJECTIVE

To investigate the association of endometrium preparation with perinatal outcomes.

DESIGN

Retrospective cohort study.

SETTING

University-affiliated fertility center.

PATIENT(S)

Twenty-one thousand six hundred and forty-eight women who underwent frozen single-blastocyst transfer from January 2013 to March 2019.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Cesarean delivery, preterm delivery (PTD), vaginal PTD, very preterm delivery (VPTD), postterm delivery, low birth weight (LBW), macrosomia, small for gestational age (SGA), large for gestational age (LGA), hypertensive disorders of pregnancy (HDP), gestational diabetes mellitus (GDM), premature rupture of membrane (PROM), placenta previa, and congenital abnormality.

RESULT(S)

Compared with natural cycles, hormone replacement cycles were associated with an increased risk of PTD, VPTD, cesarean delivery, macrosomia, PROM, and HDP. There was a trend toward an increased risk of vaginal PTD and LGA in hormone replacement cycles. Stimulated cycles were associated with an increased risk of postterm delivery and GDM. There was no statistically significant difference in the rate of SGA, placenta previa, or congenital abnormality among the three endometrium preparation methods.

CONCLUSION(S)

Hormone replacement cycles are associated with an increased risk of PTD, VPTD, cesarean delivery, LBW, macrosomia, PROM, and HDP. Stimulated cycles are associated with an increased risk of postterm delivery and GDM.

Repeated cryopreservation process impairs embryo implantation potential but does not affect neonatal outcomes

RESEARCH QUESTION

Does repeated cryopreservation process affect embryo implantation potential and neonatal outcomes of human embryos?

DESIGN

This retrospective cohort study was conducted in the Reproductive Medicine Centre, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology. All assisted reproductive technology (ART) cycles were carried out between January 2014 and December 2018. Preferentially matched participants were divided into three groups according to the times of embryo cryopreservation: the fresh group (n = 249), the cryopreservation group (n = 244) and the re-cryopreservation group (n = 216). Embryo implantation rate, live birth rate, miscarriage rate and neonatal complication rate were compared among these three groups.

RESULTS

The embryo implantation rate, clinical pregnancy rate and live birth rate in the re-cryopreservation group were significantly lower, and the miscarriage rate also slightly increased. Logistic regression analysis indicated that embryos with repeated cryopreservation and lower trophectoderm scores were at higher risk of embryo implantation failure in single embryo transfer cycles (OR 1.79 and 1.56, respectively). No significant differences were observed in gender, gestational age, birthweight, neonatal abnormality and neonatal complications among the groups.

CONCLUSIONS

Our findings demonstrate the adverse effect of repeated cryopreservation on embryo implantation potential. The study offers embryologists and reproductive clinicians a warning of detrimental role of repeated cryopreservation. If unnecessary, it is strongly recommended to avoid repeated practice of vitrification and warming on embryos.

Evidence for Corpus Luteal and Endometrial Origins of Adverse Pregnancy Outcomes in Women Conceiving with or Without Assisted Reproduction

Preeclampsia may arise from impaired decidualization in some women. Transcriptomics of mid-secretory biopsy endometrial stromal cells decidualized in vitro and of early gestation choriodecidua from women who experienced preeclampsia with severe features overlapped significantly with the classical endometrial disorders giving rise to the concept of "endometrium spectrum disorders". That is, recurrent implantation failure and miscarriage, endometriosis, normotensive intrauterine growth restriction, preeclampsia and preterm birth may all lie on a continuum of decidual dysregulation, in which phenotypic expression is determined by the specific molecular pathway(s) disrupted and severity of disruption. Women conceiving by programmed IVF protocols showed widespread dysregulation of cardiovascular function and increased rates of adverse pregnancy outcomes including preeclampsia. Programmed cycles preclude development of a corpus luteum (CL), a major regulator of endometrial function. Lack of circulating CL product(s) that are not replaced in programmed cycles (eg, relaxin) could adversely impact the maternal cardiovascular system directly and/or compromise decidualization, thereby increasing preeclampsia risk.

Perinatal and obstetric outcomes in singleton pregnancies following fresh versus cryopreserved blastocyst transfer: a meta-analysis

The transfer of cryopreserved blastocysts is increasing in IVF centres. However, little is known about the perinatal and obstetric outcomes of this procedure. In an attempt to further elucidate these issues, a systematic review and meta-analysis was conducted to compare cryopreserved transfer with fresh blastocyst embryo transfer. The results show that the risk of both preterm (odds ratio [OR] 0.89, 95% confidence interval [CI] 0.80-0.99, P = 0.04) and low birthweight births (OR 0.82, 95% CI 0.68-0.99, P = 0.04) was significantly lower after cryopreserved blastocyst transfer than after fresh blastocyst transfer. The rate of large for gestational age births was significantly higher (OR 1.68, 95% CI 1.55-1.82, P < 0.00001) and the rate of small for gestational age births significantly lower (OR 0.59, 95% CI 0.54-0.65, P < 0.00001) after cryopreserved blastocyst transfer. The transfer of cryopreserved blastocysts was associated with a significantly lower risk of placental abruption (OR 0.58, 95% CI 0.40-0.83, P = 0.003) but a significantly higher risk of Caesarean section (OR 1.21, 95% CI 1.01-1.43, P = 0.03). In conclusion, the perinatal and obstetric outcomes associated with the transfer of cryopreserved blastocysts differ from those associated with fresh blastocyst transfer.

Perinatal outcomes of singletons following vitrification versus slow-freezing of embryos: a multicenter cohort study using propensity score analysis

STUDY QUESTION

Is embryo vitrification associated with a higher risk of adverse perinatal outcomes than slow-freezing?

SUMMARY ANSWER

Embryo vitrification was not associated with increased risks of adverse perinatal outcomes of pre-term birth (PTB), low birthweight (LBW), small for gestational age (SGA), large for gestational age (LGA) and macrosomia, as compared to slow-freezing.

WHAT IS KNOWN ALREADY

Vitrification is becoming a widely adopted technology for embryo cryopreservation with higher embryo survival rate and live birth rate than the slow-freezing technique. However, limited data are currently available on risks of adverse perinatal outcomes following vitrification as compared to that of slow-freezing. The impact of vitrification on perinatal outcomes remains further to be elucidated.

STUDY DESIGN, SIZE, DURATION

Six large reproductive medical centers in Guangdong province, Southeast of China, took part in this multicenter retrospective cohort study. Cohorts of 3199 live born singletons after Day 3 frozen-thawed embryo transfer (FET) cycles with either vitrification or slow-freezing between January 2011 and December 2015 were included in the study. Each patient only contributed one cycle per cohort and vanishing twins were excluded. Propensity score (PS) matching was used to control for potential confounding factors.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All live-born singletons following either a vitrified or a slow-frozen cleavage FET cycle during the period from 2011 to 2015 were analyzed. Perinatal outcomes of PTB, LBW, macrosomia, SGA and LGA were compared. The vitrified and slow-frozen cohorts were matched by propensity scores with a 1:1 ratio accounting for potential confounding factors associated with perinatal outcomes. These variables included baseline demographics (maternal age, BMI, education level, parity, type of infertility and cause of infertility), as well as IVF characteristics (insemination method, endometrial preparation protocol and embryo cryopreservation duration).

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 2858 cases from vitrified embryo transfer (ET) and 341 babies from the slow-freezing group were included. After PS matching, 297 pairs of newborns were generated for comparison. The median gestational age was 39 weeks for both cohorts and the birthweights were comparable (3187.7 ± 502.1 g in the vitrified group vs. 3224.6 ± 483.6 in the slow-freezing group, P>0.05). There were no significant differences between the two groups on the incidence of PTB (5.4% vs. 7.7%), LBW (6.7% vs. 5.7%), macrosomia (5.7% vs. 6.1%), SGA (12.5% vs. 8.4%) and LGA (6.4% vs. 8.1%). Parallel logistic regression analysis indicated that vitrification was non-inferior to slow-freezing method in terms of the occurrence of PTB (OR, 0.68 [95% CI, 0.35, 1.31]), LBW (OR, 1.19[0.61-2.32]), macrosomia (OR, 0.94 [0.48-1.86]), SGA (1.55[0.91-2.64]) and LGA (0.78[0.42-1.45]), P>0.05. Sex-stratified PS matching models with multivariable regression analysis further confirmed that vitrification did not increase the risks of above-mentioned adverse perinatal outcomes in either the male or female infant cohort.

LIMITATIONS, REASONS FOR CAUTION

Although the analysis was adjusted for a number of important confounders, the hospital dataset did not contain other potential confounders such as the medical history and obstetrics outcomes of women during pregnancy to allow adjustment. In addition, the current findings are only applicable to cleavage stage FET, but not pronuclei stage or blastocyst stage ET.

WIDER IMPLICATIONS OF THE FINDINGS

Vitrified ET, in comparison with slow-frozen ET, was not associated with increased risks of adverse neonatal outcomes. With its superiority on live birth rates and non-inferiority on safety perinatal outcomes, transition from slow-freezing to the use of vitrification for embryo cryopreservation is reassuring. Nonetheless, future research is needed for the long-term effects of vitrification method on offspring's health outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the National Key Research and Development Program (2016YFC100205), Guangzhou Science and Technology Project (201804020087), Guangdong Province Science and Technology Project (2016A020218008) and Guangdong Provincial Key Laboratory of Reproductive Medicine (2012A061400003). The authors have no conflicts of interest to declare.

Number of embryos transferred and diagnosis of preeclampsia

BACKGROUND

Multiple births and first pregnancy are associated with higher preeclampsia risk. It is unknown if the transfer of multiple embryos or first embryo transfer with assisted reproductive technology (ART) is also associated with greater preeclampsia risk.

METHODS

We performed a retrospective cohort study of IVF clinics and hospitals in Massachusetts. We used linked ART surveillance, birth certificate, and maternal hospitalization discharge data for 21,188 births, considering resident singleton (12,810) and twin (8378) live-births from autologous or donor eggs from 2005 to 2012. We used log binomial and Poisson regression to calculate adjusted relative risks (aRRs) and 95% confidence intervals (CI) for the association between preeclampsia and predictors of preeclampsia. Outcomes were stratified by singleton and twin birth, donor versus autologous cycles, and use of fresh versus cryopreserved embryos.

RESULTS

Considering all singleton births, the transfer of multiple embryos increased the risk of preeclampsia [aRR = 1.10 (95% CI: 1.01-1.19)]. Relative risks were greatest for fresh non-donor cycles [aRR = 1.14 (95% CI: 1.03-1.26)]. Vanishing twin and number of prior ART cycles was not associated with preeclampsia among singleton births [aRR = 1.18 (95% CI: 0.91-1.53)], and aRR = 1.01 (95% CI: 0.96-1.05)], respectively. Considering all twin births, the transfer of > 2 embryos increased the risk of preeclampsia [aRR = 1.09 (95% CI: 1.001-1.19)]. Vanishing triplet and number of prior ART cycles were not associated with preeclampsia among twin births [aRR = 0.93 (95% CI: 0.69-1264), and aRR = 0.98 (CI: 0.95-1.02)], respectively.

CONCLUSIONS

Among ART births, the transfer of more than 1 embryo for singleton gestations and more than 2 embryos for twin gestations increased the risk for preeclampsia diagnosis.

The Future of Cryopreservation in Assisted Reproductive Technologies

Societal changes and the increasing desire and opportunity to preserve fertility have increased the demand for effective assisted reproductive technologies (ART) and have increased the range of scenarios in which ART is now used. In recent years, the "freeze-all" strategy of cryopreserving all oocytes or good quality embryos produced in an IVF cycle to transfer later-at a time that is more appropriate for reasons of medical need, efficacy, or desirability-has emerged as an accepted and valuable alternative to fresh embryo transfer. Indeed, improvements in cryopreservation techniques (vitrification) and the development of more efficient ovarian stimulation protocols have facilitated a dramatic increase in the practice of elective frozen embryo transfer (eFET). Alongside these advances, debate continues about whether eFET should be a standard treatment option available to the whole IVF population or if it is important to identify patient subgroups who are most likely to benefit from such an approach. Achieving successful outcomes in ART, whether by fresh or frozen embryo transfer, is influenced by a wide range of factors. As well as the efficiency of IVF and embryo transfer protocols and techniques, factors affecting implantation include maternal aging, sperm quality, the vaginal and endometrial microbiome, and peri-implantation levels of serum progesterone. The safety of eFET, both during ART cycles and on longer-term obstetric and neonatal outcomes, is also an important consideration. In this review, we explore the benefits and risks of freeze-all strategies in different scenarios. We review available evidence on the outcomes achieved with elective cryopreservation strategies and practices and how these compare with more traditional IVF cycles with fresh embryo transfers, both in the general IVF population and in subgroups of special interest. In addition, we consider how to optimize and individualize "freeze-all" procedures to achieve successful reproductive outcomes.

Risk of ischemic placental disease in fresh and frozen embryo transfer cycles

OBJECTIVES

To evaluate the association of fresh and frozen embryo transfer with the development of ischemic placental disease (IPD), hypothesizing that differences in implantation environment affect placentation and thus pregnancy outcomes.

DESIGN

We performed a secondary analysis of a retrospective cohort study of deliveries linked to IVF cycles.

SETTING

Tertiary hospital and infertility treatment center.

PATIENT(S)

We included all women who underwent an autologous IVF cycle and had a live-born infant or an intrauterine fetal demise (IUFD). We excluded women less than 18 years of age.

INTERVENTION(S)

We compared pregnancies resulting from frozen embryo transfer (frozen) cycles with those resulting from fresh embryo transfer (fresh) cycles.

MAIN OUTCOME MEASURE(S)

The primary outcome was a composite outcome of IPD or IUFD due to placental insufficiency. Ischemic placental disease included pre-eclampsia, placental abruption, and small for gestational age (SGA). We calculated risk ratios (RRs) and 95% confidence intervals (CIs).

RESULT(S)

Compared with fresh cycles, frozen cycles had a lower risk of IPD or IUFD from placental insufficiency (RR 0.75, 95% CI 0.59-0.97). Frozen cycles also conferred a lower risk of SGA than fresh cycles (RR 0.58, 95% CI 0.41-0.81). Risks of pre-eclampsia (RR 1.3, 95% CI 0.84-1.9) and abruption (RR 1.2, 95% CI 0.56-2.4) were similar.

CONCLUSION(S)

There was a lower risk of IPD among frozen cycles compared with fresh cycles. This association was largely driven by lower risk of SGA among frozen cycles.

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.

Single fresh blastocyst transfer or single cryopreserved-thawed blastocyst transfer: which is preferable for infertile patients in IVF/ICSI cycles? A meta-analysis

PURPOSES

Nowadays, an increasing number of studies have proposed single embryo transfer (SET), especially single blastocyst transfer (SBT). To compare the clinical outcomes of single fresh blastocyst transfer (BT) and single cryopreserved-thawed BT in patients undergoing in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) cycles.

METHODS

The PubMed, Embase, and Cochrane Library databases were searched from the start dates until February 2018. The primary outcomes were clinical pregnancy rate (CPR) and embryo implantation rate (IR). The secondary outcomes were multiple pregnancy rate (MPR), live birth rate (LBR), and miscarriage rate (MR). Using the Mantel-Haenszel random effects model to analyze summary risk ratio (RR) with 95% confidence intervals (CIs). Statistical heterogeneity scores were assessed with the standard Cochrane's Q test and I² statistic.

RESULTS

In total, eight studies (two prospective studies, six retrospective studies) were included in our analysis. There was no statistically significant difference regarding clinical pregnancy (RR = 1.18, 95% CI = 0.91-1.55) and embryo implantation (RR = 1.04, 95% CI = 0.77-1.41). Regarding secondary outcomes, there was no significant difference regarding miscarriage (RR = 0.79, 95% CI = 0.60-1.03) and multiple pregnancy (RR = 1.23, 95% CI = 0.75-2.04). However, single fresh BT is associated with an increased live birth (RR = 1.28, 95% CI = 1.05-1.57) compared with single cryopreserved-thawed BT.

CONCLUSIONS

In summary, this meta-analysis supports the hypothesis that single cryopreserved BT might not be the best choice compared with single fresh BT in patients undergoing IVF/ICSI cycles.

Comparison of perinatal outcomes following frozen embryo transfer cycles using autologous versus donor oocytes in women 40 to 43 years old: analysis of SART CORS data

OBJECTIVE

To study the differences in perinatal outcomes after frozen embryo transfer cycles using autologous or donor oocytes in women of advanced maternal age.

DESIGN

Historical cohort study.

SETTING

US national database from the Society of Assisted Reproductive Technology Clinic Outcome Reporting System (SART CORS) from 2009 to 2013.

PATIENT(S)

Women at 40-43 years of age undergoing autologous frozen embryo transfers (a-FET) or donor oocyte frozen embryo transfers (d-FET) resulting in singleton pregnancies that were entered in the SART CORS database from 2009 to 2013.

RESULTS

a-FET resulted in 4402 singleton live births whereas d-FET resulted in 2703 singleton live births. d-FET resulted in a higher risk of preterm births (< 37 weeks), with adjusted odds ratio (aOR) 1.33 (95% CI 1.02-1.75), but similar risk of small for gestational age (SGA), with aOR 1.75 (95% CI 0.85-3.7), when compared to a-FET. However, when only single blastocyst transfer cycles are considered, d-FET and a-FET showed no difference in preterm births or other adverse perinatal outcomes.

CONCLUSIONS

Singletons resulting from d-FET are at increased risk for perinatal morbidity. However, the risk was diminished in single blastocyst transfer cycles. Our study supports the current American Society for Reproductive Medicine (ASRM) guidelines of transferring a single blastocyst in d-FET cycles.

Risk of preeclampsia in pregnancies resulting from double gamete donation and from oocyte donation alone

INTRODUCTION

Pregnancies after gamete donation are at higher risk of developing pre-eclampsia (PE) than those achieved by IVF with patient's own gametes. We aim to assess whether pregnancies achieved with both oocyte and sperm donation (double donation, DD) are at an increased risk of developing PE and gestational hypertension (GH) compared to those achieved by oocyte donation alone (OD).

MATERIALS AND METHODS

Retrospective cohort study of 433 patients who reached the 20th week of gestation with either DD (n = 81) or OD (n = 352) between March 2013 and April 2016 at a fertility clinic. The risk of preterm PE, term PE, and gestational hypertension (GH) are presented as unadjusted and adjusted odds ratio (OR).

RESULTS

DD have a higher risk of preterm PE than OD, with an OR of 3.02 (95%CI 1.11-8.24; p = 0.031). We found no difference in the risk of term PE (OR 0.26, 95%CI 0.03-1.98; p = 0.19) or of GH (OR 1.23, 95% CI 0.63-2.43; p = 0.55).

DISCUSSION

Pregnancies with DD are at higher risk of developing preterm PE than OD alone. Patients, and physicians treating them, should be made aware of the elevated risk of PE in these gestations, in order to start prophylactic measures during the first weeks of pregnancy.

Birthweight in infants conceived through in vitro fertilization following blastocyst or cleavage-stage embryo transfer: a national registry study

PURPOSE

In vitro fertilization (IVF) infants have lower birthweights than their peers, predisposing them to long-term health consequences. Blastocyst transfer (BT), at day 5-6 post-fertilization, is increasing in usage, partially due to improved pregnancy outcomes over cleavage-stage transfer (CT, day 2-3). Data to date, however, have been inconclusive regarding BT's effects on birthweight.

METHODS

Participants included all US autologous, single-gestation, fresh embryo transfer cycles initiated from 2007 to 2014 that resulted in a term infant (N = 124,154) from the National Assisted Reproductive Technology Surveillance System. Generalized linear models including obstetric history, maternal demographics, and infant sex and gestational age were used to compare birthweight outcomes for infants born following BT (N = 67,169) with infants born following CT (N = 56,985) and to test for an interaction between transfer stage and single embryo transfer (SET).

RESULTS

Infants born following BT were 6 g larger than those born following CT (p = 0.04), but rates of macrosomia (RR 1.00, 95% CI 0.96-1.04) and low birthweight (LBW, RR 1.00, 95% CI 0.93-1.06) were not different between the groups. The interaction between SET and transfer stage was significant (p = 0.02). Among SET infants, BT was associated with 19.26 g increased birthweight compared to CT (p = 0.008).

CONCLUSIONS

The increase in birthweights identified following BT is unlikely to be clinically relevant, as there were no differences in rates of macrosomia or LBW. These findings are clinically reassuring and indicate that the increasing use of BT is unlikely to further decrease the on average lower birthweights seen in IVF infants compared to their naturally conceived peers.

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.

Embryo cryopreservation and preeclampsia risk

OBJECTIVE

To determine whether assisted reproductive technology (ART) cycles involving cryopreserved-warmed embryos are associated with the development of preeclampsia.

DESIGN

Retrospective cohort study.

SETTING

IVF clinics and hospitals.

PATIENT(S)

A total of 15,937 births from ART: 9,417 singleton and 6,520 twin.

INTERVENTION(S)

We used linked ART surveillance, birth certificate, and maternal hospitalization discharge data, considering resident singleton and twin births from autologous or donor eggs from 2005-2010.

MAIN OUTCOME MEASURE(S)

We compared the frequency of preeclampsia diagnosis for cryopreserved-warmed versus fresh ET and used multivariable logistic regression to adjust for confounders.

RESULT(S)

Among pregnancies conceived with autologous eggs resulting in singletons, preeclampsia was greater after cryopreserved-warmed versus fresh ET (7.51% vs. 4.29%, adjusted odds ratio = 2.17 [95% CI 1.67-2.82]). Preeclampsia without and with severe features, preeclampsia with preterm delivery, and chronic hypertension with superimposed preeclampsia were more frequent after cryopreserved-warmed versus fresh ET (3.99% vs. 2.55%; 2.95% vs. 1.41%; 2.76 vs. 1.48%; and 0.95% vs. 0.43%, respectively). Among pregnancies from autologous eggs resulting in twins, the frequency of preeclampsia with severe features (9.26% vs. 5.70%) and preeclampsia with preterm delivery (14.81% vs. 11.74%) was higher after cryopreserved versus fresh transfers. Among donor egg pregnancies, rates of preeclampsia did not differ significantly between cryopreserved-warmed and fresh ET (10.78% vs. 12.13% for singletons and 28.0% vs. 25.15% for twins).

CONCLUSION(S)

Among ART pregnancies conceived using autologous eggs resulting in live births, those involving transfer of cryopreserved-warmed embryos, as compared with fresh ETs, had increased risk for preeclampsia with severe features and preeclampsia with preterm delivery.

Comparison of pregnancy outcomes after vitrification at the cleavage and blastocyst stage: a meta-analysis

OBJECTIVE

This systematic review sought to evaluate the clinical outcomes of vitrification at the cleavage stage and blastocyst stage for embryo transfer in patients undergoing assisted reproductive technology (ART) treatment.

METHODS

We searched for related comparative studies published in the PubMed, EMBASE, and Cochrane Library databases up to July 2017. The primary outcomes were clinical pregnancy rate (CPR) and embryo implantation rate (IR). Secondary outcomes were multiple pregnancy rate (MPR), miscarriage rate (MR), live birth rate (LBR), and ongoing pregnancy rate (OPR). The Mantel-Haenszel fixed effects model and random effects model were used to analyze the summary risks ratios (RRs) with 95% confidence intervals (CIs).

RESULTS

Eight studies with more than 6590 cycles were included in our meta-analysis. Seven studies were observational retrospective comparative studies. One was a prospective study. Overall, the current study summarizes information from 6590 vitrification warming cycles (cleavage stage n = 4594; blastocysts n = 1996). There was no difference in the primary outcome clinical pregnancy rate (RR = 0.97, 95% CI = 0.90-1.04; fixed effects model; I ²  = 21%), whereas vitrified blastocyst transfer was significantly superior to vitrified cleavage-stage embryo transfer regarding the implantation rate (RR = 0.85, 95% CI = 0.74-0.97; random effects model; I ²  = 43). Regarding the secondary outcomes, no differences were found in the multiple pregnancy rate (RR = 1.20, 95% CI = 0.79-1.82; fixed effects model; I ²  = 22), live birth rate (RR = 1.07, 95% CI = 0.98-1.16; fixed effects model; I ²  = 0), and ongoing pregnancy rate (RR = 1.01, 95% CI = 0.92-1.120; fixed effects model; I ²  = 0), whereas a higher miscarriage rate was observed with vitrified blastocyst transfer (RR = 0.65, 95% CI = 0.45-0.93; random effects model; I ²  = 23).

CONCLUSION

In summary, this meta-analysis shows that vitrification at any stage has no detrimental effect on clinical outcome. Blastocyst transfer will still remain a favorable and promising option in ART. Due to the small sample evaluated in the pool of included studies, large-scale, prospective, and randomized controlled trials are required to determine if these small effects are clinically relevant.

Genome-wide microRNA expression profiling in placentae from frozen-thawed blastocyst transfer

Background

Frozen-thawed embryo transfer (FET) is increasingly available for the improvement of the success rate of assisted reproductive technologies other than fresh embryo transfer (ET). There have been numerous findings that FET provides better obstetric and perinatal outcomes. However, the birth weight of infants conceived using FET is heavier than that of those conceived via ET. In addition, some reports have suggested that FET is associated with perinatal diseases such as placenta accreta and pregnancy-induced hypertension (PIH).

Results

In this study, we compared the microRNA (miRNA) expression profiles in term placentae derived from FET, ET, and spontaneous pregnancy (SP). We identified four miRNAs, miR-130a-3p, miR-149-5p, miR-423-5p, and miR-487b-3p, that were significantly downregulated in FET placentae compared with those from SP and ET. We found that DNA methylation of MEG3-DMR, not but IG-DMR, was associated with miRNA expression of the DLK1-DIO3 imprinted domain in the human placenta. In functional analyses, GO terms and signaling pathways related to positive regulation of gene expression, growth, development, cell migration, and type II diabetes mellitus (T2DM) were enriched.

Conclusions

This study supports the hypothesis that the process of FET may increase exposure of epigenome to external influences.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0379-6) contains supplementary material, which is available to authorized users.

Abnormal implantation after fresh and frozen in vitro fertilization cycles

OBJECTIVE

To determine whether fresh embryo transfers are at a higher risk of abnormal implantation compared with frozen embryo transfers while accounting for the embryo stage at transfer.

DESIGN

Retrospective cohort study.

SETTING

Not applicable.

PATIENT(S)

We used data from the Society for Assisted Reproductive Technologies to identify all fresh and frozen autologous IVF cycles from 2004-2013 resulting in a positive pregnancy test. The cycles were parameterized into a four-level predictor of [1] fresh blastocyst transfer, [2] fresh non-blastocyst transfer, [3] frozen blastocyst transfer, and [4] frozen non-blastocyst transfer.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

We examined a composite outcome of abnormal implantation, defined as biochemical pregnancy, ectopic/heterotopic pregnancy, and first-trimester pregnancy loss. Regression modeling was performed with repeated measures multivariable logistic regression, adjusted for age, parity, number of embryos transferred, infertility diagnosis, and calendar year of treatment.

RESULT(S)

Of 509,938 cycles analyzed, 31.8% resulted in abnormal implantation. Compared with a fresh blastocyst transfer, a fresh non-blastocyst transfer had a 22% increase risk of abnormal implantation, a frozen blastocyst transfer had a 36% increase risk, and a frozen non-blastocyst transfer had a 57% increase risk. When individual outcomes were analyzed, fresh embryo transfers had a lower risk of biochemical pregnancy and pregnancy loss but a higher risk for ectopic/heterotopic pregnancy.

CONCLUSION(S)

Fresh blastocyst transfers had the lowest overall risk of abnormal implantation but a higher risk of ectopic/heterotopic pregnancy. Although embryo cryopreservation is indicated in certain treatment cycles, elective embryo cryopreservation may not be the optimal strategy to adopt for all cycles.

Assisted Reproductive Technology and Newborn Size in Singletons Resulting from Fresh and Cryopreserved Embryos Transfer

OBJECTIVES AND STUDY DESIGN

The aim of this study was two-fold: to investigate the association of Assisted Reproductive Technology (ART) and small newborn size, using standardized measures; and to examine within strata of fresh and cryopreserved embryos transfer, whether this association is influenced by parental infertility diagnoses. We used a population-based retrospective cohort from Michigan (2000-2009), Florida and Massachusetts (2000-2010). Our sample included 28,946 ART singletons conceived with non-donor oocytes and 4,263,846 non-ART singletons.

METHODS

Regression models were used to examine the association of ART and newborn size, measured as small for gestational age (SGA) and birth-weight-z-score, among four mutually exclusive infertility groups: female infertility only, male infertility only, combined female and male infertility, and unexplained infertility, stratified by fresh and cryopreserved embryos transfer.

RESULTS

We found increased SGA odds among ART singletons from fresh embryos transfer compared with non-ART singletons, with little difference by infertility source [adjusted odds-ratio for SGA among female infertility only: 1.18 (95% CI 1.10, 1.26), male infertility only: 1.20 (95% CI 1.10, 1.32), male and female infertility: 1.18 (95% CI 1.06, 1.31) and unexplained infertility: 1.24 (95% CI 1.10, 1.38)]. Conversely, ART singletons, born following cryopreserved embryos transfer, had lower SGA odds compared with non-ART singletons, with mild variation by infertility source [adjusted odds-ratio for SGA among female infertility only: 0.56 (95% CI 0.45, 0.71), male infertility only: 0.64 (95% CI 0.47, 0.86), male and female infertility: 0.52 (95% CI 0.36, 0.77) and unexplained infertility: 0.71 (95% CI 0.47, 1.06)]. Birth-weight-z-score was significantly lower for ART singletons born following fresh embryos transfer than non-ART singletons, regardless of infertility diagnoses.