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

Perinatal outcomes of singletons following double vitrification-warming procedures: a retrospective study using propensity score analysis

BACKGROUND

Although repeated cryopreservation is an occasional occurrence, the effect on perinatal outcomes is unclear. Therefore, the aim of this study was to evaluate the perinatal outcomes of singletons after embryo re-cryopreservation.

METHODS

In this retrospective study, a total of 647 singleton live births after blastocyst freeze-thaw embryo transfer cycles were investigated. They were divided into two groups: vitrified-warmed blastocysts (once-vitrified group) and vitrified-warmed blastocysts derived from thawed cleaved embryos (re-vitrified group). Propensity score matching (PSM) was used to control for potential confounding factors.

RESULTS

A total of 592 infants were included in the once-vitrified group, and 55 infants were included in the re-vitrified group. After PSM, 108 cases were generated for comparison. The median gestational age was 38 weeks for both groups, and the birthweights were comparable (3390.6 ± 601.5 g vs. 3412.8 ± 672.6 g, P > 0.05). The incidence of preterm birth (PTB) (20.4% vs. 16.7%), low birthweight (LBW) (3.7% vs. 7.4%), macrosomia (11.1% vs. 16.7%) and large for gestational age (LGA) (29.6% vs. 22.2%) were not significantly different between the two groups. Logistic regression analysis indicated that double vitrification-warming procedures did not affect the occurrence of PTB (OR, 2.58 [95% CI, 0.77, 8.63]), LBW (OR, 0.83 [95% CI, 0.08, 8.29]), macrosomia (OR, 0.60 [95% CI, 0.13, 2.69]), or LGA (OR, 1.51 [95% CI, 0.53, 4.27]) (P > 0.05, for all).

CONCLUSION

Our findings demonstrate that double vitrification-warming procedures do not increase the risk of adverse neonatal outcomes compared with those of once-vitrified embryos.

Clinical and perinatal outcomes of fresh single-blastocyst-transfer cycles under an early follicular phase prolonged protocol according to day of trigger estradiol levels

Backgroud

This study’s objectives were to compare the clinical, perinatal, and obstetrical outcomes of patients with different estradiol (E₂) levels in fresh single-blastocyst-transfer (SBT) cycles under an early follicular phase prolonged regimen on the day of trigger.

Methods

We recruited patients in fresh SBT cycles (n = 771) undergoing early follicular phase prolonged protocols with β-hCG values above 10 IU/L between June 2016 and December 2018. Patients who met the inclusion and exclusion criteria were divided into four groups according to their serum E₂ level percentages on the day of trigger: <25^th, 25^th–50^th, 51^st–75^th, and >75^th percentile groups.

Results

Although the rates of clinical pregnancy (85.57% (166/194)), embryo implantation 86.60% (168/194), ongoing pregnancy (71.13% (138/194)), and live birth (71.13% (138/194)) were lowest in the >75th percentile group, we did not observe any significant differences (all P > 0.05). We used this information to predict the rate of severe ovarian hyperstimulation syndrome (OHSS) area under the curve (AUC) = 72.39%, P = 0.029, cut off value of E₂ = 2,893 pg/ml with the 75% sensitivity and 70% specificity. The 51^st–75^th percentile group had the highest rates of low birth weight infants (11.73% (19/162), P = 0.0408), premature delivery (11.43% (20/175), P = 0.0269), admission to the neonatal intensive care unit (NICU) (10.49% (17/162), P = 0.0029), twin pregnancies (8.57% (15/175), P = 0.0047), and monochorionic diamniotic pregnancies (8.57% (15/175); P = 0.001). We did not observe statistical differences in obstetrics complications, including gestational diabetes mellitus (GDM), gestational hypertension, placenta previa, premature rupture of membranes (PROM), and preterm premature rupture of membranes (PPROM).

Conclusion

We concluded that serum E₂ levels on the day of trigger were not good predictors of live birth rate or perinatal and obstetrical outcomes. However, we found that high E₂ levels may not be conducive to persistent pregnancies. The E₂ level on the day of trigger can still be used to predict the incidence of early onset severe OHSS in the fresh SBT cycle.

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.

Comparison of the Method of Endometrial Preparation Prior to Frozen-Thawed Embryo Transfer: a Retrospective Cohort Study from 9733 Cycles

Our objective was to compare the effectiveness of natural cycles (NC), modified natural cycle (mNC), and artificial cycles (AC) in women undergoing frozen-thawed embryo transfer (FET) after in vitro fertilization (IVF). This is a retrospective cohort study analyzing 9733 women undergoing the first cycle of FET over a 3-year period (June 2014-December 2017) at Northwest Women's and Children's Hospital after IVF-ICSI cycles. The type of endometrial preparation was determined by the treating physician's preference, based on patients' characteristics. Women with regular ovulation were allocated to natural cycles (n = 1480) or modified natural cycles (n = 196) when the leading follicle was triggered with hCG, while patients who were reluctant to frequently monitoring or living far from the hospital were allocated to artificial cycles (n = 8057). A logistic regression model was used to assess the association between endometrial preparation and clinical outcomes while adjusting for potential confounders. Live birth rate was primary outcome while miscarriage rate, clinical pregnancy rate, preterm birth rate, and ectopic pregnancy rate were secondary outcomes. In the adjusted model, type of endometrial preparation did not affect live birth (OR, 0.89; 95% CI, 0.74-0.96), clinical pregnancy (OR, 0.93; 95% CI, 0.81-1.06), preterm birth (OR, 1.03; 95% CI, 0.84-1.26), and ectopic pregnancy (OR, 0.73; 95% CI, 0.33-1.59), while AC significantly increased the miscarriage rate (OR, 1.49; 95% CI, 1.17-1.89, P=0.001). In conclusions, in women undergoing FET, natural cycles and artificial cycles resulted in comparable live birth rate while miscarriage rate was higher in artificial cycles.

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.

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.

Which is better for mothers and babies: fresh or frozen-thawed blastocyst transfer?

BACKGROUND

In recent years, there have been many reports on the pregnancy outcomes of fresh blastocyst transfer (BT) and frozen-thawed BT, but the conclusions are controversial and incomplete. To compare the pregnancy outcomes, maternal complications and neonatal outcomes of fresh and frozen-thawed BT in the context of in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) cycles, we conducted a meta-analysis.

METHODS

A meta-analysis was conducted by searching the PubMed, Embase, and Cochrane Library databases through May 2020. Data were extracted independently by two authors.

RESULTS

Fifty-four studies, including 12 randomized controlled trials (RCTs), met the inclusion criteria. Fresh BT was associated with a lower implantation rate, pregnancy rate, ongoing pregnancy rate, and clinical pregnancy rate and higher ectopic pregnancy rate than frozen-thawed BT according to the results of the RCTs. The risks of moderate or severe ovarian hyperstimulation syndrome, placental abruption, placenta previa and preterm delivery were higher for fresh BT than for frozen-thawed BT. The risk of pregnancy-induced hypertension and pre-eclampsia was lower for fresh BT; however, no significant differences in risks for gestational diabetes mellitus and preterm rupture of membrane were found between the two groups. Compared with frozen-thawed BT, fresh BT appears to be associated with small for gestational age and low birth weight. No differences in the incidences of neonatal mortality or neonatal malformation were observed between fresh and frozen-thawed BT.

CONCLUSIONS

At present there is an overall slight preponderance of risks in fresh cycles against frozen, however individualization is required and current knowledge does not permit to address a defintive response.

Transfers of lower quality embryos based on morphological appearance result in appreciable live birth rates: a Canadian center's experience

Objective

To determine the reproductive outcomes resulting from transfer of lower-grade blastocysts to support the practice of cryopreserving and transferring lower-grade embryos.

Design

Retrospective chart review.

Setting

Single infertility center.

Patient(s)

Women who have undergone a fresh (n = 570) or frozen (n = 885) transfer of a single blastocyst embryo between December 2013 and December 2018.

Intervention(s)

None.

Main Outcome Measure(s)

The primary outcome was live birth rate. The secondary outcomes included implantation rate, ongoing pregnancy rate, associations with inner cell mass (ICM) and trophectoderm epithelium (TE) grades determined by morphological assessment, and antenatal/perinatal complications.

Results

Reproductive outcomes directly correlated with embryo quality. Transfers of AA embryos resulted in a 41.4% live birth rate compared to 31.1% for BB embryos and 13.3% for CC embryos. The TE grade was significantly associated with the live birth rate. Embryos with a TE grade of “B” had an odds ratio of 0.677 and embryos with a TE grade of “C” had an odds ratio of 0.394 compared to embryos with a TE grade of “A” for live birth.

Conclusion

Embryos with a TE “C” grade should be considered for transfer and cryopreservation, as they are shown to result in appreciable live birth rates. Such treatment should involve a thorough discussion with patients, however, as these live birth rates are significantly lower than those associated with higher-grade embryos.

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.

Obstetric and perinatal outcomes of pregnancies according to initial maternal serum HCG concentrations after vitrified-warmed single blastocyst transfer

RESEARCH QUESTION

Do pregnancy, obstetric and perinatal outcomes differ according to initial maternal serum human chorionic gonadotrophin (HCG) level measured on day 11 after single blastocyst transfer?

DESIGN

Vitrified-warmed single blastocyst transfer cycles (n = 640) were collected between 1 January 2013 and 30 April 2017 with positive HCG values and retrospectively analysed by receiver operating characteristic curves to predict clinical pregnancy, ongoing pregnancy and delivery. Cycles were divided into a low HCG group (n = 155) and high HCG group (n = 485) based on cut-off value of live birth prediction. Cycles in the HCG group were subdivided into a low-high subgroup (n = 162), medium-high subgroup (n = 162) and high-high subgroup (n = 161) based on tertile points. Pregnancy rates and obstetric and perinatal outcomes were compared.

RESULTS

The area under curves for clinical pregnancy, ongoing pregnancy and live birth prediction were 0.95, 0.81 and 0.79, respectively; corresponding cut-off values were 152.2 IU/l, 211.9 IU/l and 211.9 IU/l; HCG less than 211.9 IU/l indicated an extremely low clinical pregnancy rate (34.84%), a high early miscarriage rate (61.11%) and a low live birth rate (12.26%). Rates of gestational diabetes mellitus (GDM) (P = 0.007) and female neonates (P = 0.001) were significantly higher in the LHG group compared with the HHG group; no significant differences were observed in the low versus high HCG group overall.

CONCLUSIONS

Lower initial maternal serum HCG levels indicated poorer clinical outcomes. Within the high HCG group, a lower initial maternal HCG level was found to be associated with GDM occurrence and proportion of female neonates.

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.