STUDY QUESTION Does the quality of a single transferred blastocyst affect singleton birthweight in frozen-embryo transfer (FET) cycles? SUMMARY ANSWER The transfer of a poor-quality blastocyst was associated with lower mean birthweight and gestation-adjusted birthweight (Z-scores) when compared with the transfer of an excellent-quality blastocyst during FET cycles. WHAT IS KNOWN ALREADY Embryo quality is a strong predictor of IVF success rates. However, very few studies have examined the effect of embryo quality on singleton birthweight. STUDY DESIGN, SIZE, DURATION This retrospective study involved singleton live births born to women undergoing frozen-thawed single blastocyst transfers during the period from January 2010 to December 2017 at a tertiary care centre. PARTICIPANTS/MATERIALS, SETTING, METHODS A total of 1207 women who fulfilled the inclusion criteria were included and were grouped into four groups depending on the blastocyst quality: excellent, good, average and poor. The primary outcome measure was singleton birthweight. The Z-score was employed to calculate the birthweight adjusted for gestational age and newborn gender. Multiple linear regression analysis was performed to investigate the relationship between embryo quality and neonatal birthweight after adjustment for some potential confounders. MAIN RESULTS AND THE ROLE OF CHANCE In the primary multivariable model, singletons from the poor-quality blastocyst group weighed 183.5 g less than those from the excellent-quality blastocyst group (95% CI: −295.1 to −71.9 g, P = 0.001) in terms of mean birthweight after accounting for patient characteristics, IVF treatment parameters, the year of treatment and newborn gender. Likewise, poor-quality blastocyst transfer was associated with lower gestation-adjusted Z-scores than the transfer of excellent-quality blastocysts (β = −0.35, 95% CI: −0.59 to −0.12, P = 0.003). LIMITATIONS AND REASONS FOR CAUTION The current study was limited by its retrospective design and the fact that our analysis was restricted to women with singleton births from single blastocyst transfers. Future prospective studies are required to confirm our findings. WIDER IMPLICATIONS OF THE FINDINGS Our findings provide new insight into the relationship between embryo quality and neonatal outcomes by showing that poor-quality blastocyst transfer was associated with a decrease in singleton birthweight. STUDY FUNDING/COMPETING INTEREST(S) This study was supported by the National Key Research and Development Program of China (grant no. 2018YFC1003000), the National Natural Science Foundation of China (grant nos. 81771533, 81571397 and 31770989), and the China Postdoctoral Science Foundation (Grant no. 2018M630456). The authors have no conflicts of interest to declare. TRIAL REGISTRATION NUMBER Not applicable.
Background: Extended embryo culture has been reported to affect perinatal outcome regarding higher risks of large for gestational age (LGA) and preterm birth (PTB) yet decreased risk of small for gestational age (SGA). However, existing data about the obstetric outcome and the safety for offspring resulting from the transfer of day 7 blastocysts is rare. Objectives: To compare obstetric and perinatal outcome using embryos vitrified on day 7 with those vitrified on day 3, day 5, and day 6. Methods: Data were collected from 4489 infertile women who gave birth to liveborn singletons after vitrified-warmed embryo transfer cycles from January 1, 2006 to December 31, 2017. Singletons were compared depending on the age of embryos. Main perinatal outcome parameters included PTB (gestational age < 37 weeks), very PTB (VPTB, gestational age < 32 weeks), LGA (birthweights > 90th percentiles), and SGA (birthweights < 10th percentiles). Obstetric outcomes included gestational diabetes (GDM), pregnancy-induced hypertension (PIH), preterm premature rupture of membranes (PPROM), pre-eclampsia, placenta previa, placental abruption, and postpartum hemorrhage. Propensity score matching (PSM) was used to adjust the confounding factors across groups and then analyze the association between in vitro culture period and the outcome measures. Results: After PSM, the transfer of day 7 blastocysts was associated with higher birth weight Z-scores and increased incidence of very large for gestational age (VLGA) compared with the transfer of day 3 cleavage-stage embryos while the incidence of PTB, low birth weight (LBW), SGA did not reach statistical significance. Moreover, comparable perinatal outcome was found in the comparison of day 7 vs. day 5 and day 7 vs. day 6. Day 7 blastocysts did not result in adverse obstetric outcome compared with day 3, day 5, and day 6 embryos, respectively. Conclusion: In vitrified-warmed transfer cycles, day 7 blastocysts were associated with adverse perinatal outcome regarding higher risk of VLGA compared with day 3 cleavage-stage embryo, while blastocysts with diverse growth rates embrace similar developmental viability regardless of blastocysts vitrified on day 5, day 6, or day 7.
Background: Previous studies have reported the association between embryo quality and perinatal outcomes in fresh cycles, after cleavage-stage or blastocyst embryo transfer, and found no significant difference. However, in terms of vitrified-warmed embryo transfer cycles, the impact of embryo quality on neonatal and maternal outcomes has not been evaluated.Objectives: To explore the association between the quality of a single vitrified-warmed embryo and perinatal outcomes.Methods: This retrospective study included 2403 live-born singletons derived from single vitrified-warmed embryo transfer cycles during January 2006 and July 2018. Neonatal and maternal outcomes were compared between singletons resulting from the use of single good quality embryo (GQE) (n = 1854) and single poor quality embryo (PQE) (n = 549) and analyzed in the group of cleavage-stage embryo transfer and the group of blastocyst transfer, respectively.Results: A significantly higher risk of low birthweight (LBW, birthweight <2500 g) was observed in the singletons derived from the transfer of single PQE compared with those derived from the transfer of single GQE both in cleavage and blastocyst stages (cleavage-stage, AOR 2.62, 95% CI 1.27-5.37; blastocyst stage, AOR 1.98, 95% CI 1. 06-3.70). An increased risk of preterm birth (PTB, gestational age <37 weeks) was also observed in singletons born after transfer of a PQE of cleavage-stage compared with those after a GQE of cleavage-stage (AOR 2.40, 95% CI 1.28-4.49). The transfer of single poor quality blastocyst was associated with a higher risk of placenta previa compared with the transfer of single good quality blastocyst (AOR 2.65, 95% CI 1.26-5.57). Other maternal complications, neonatal malformations, and neonatal complications were similar between compared groups. Conclusion:In vitrified-warmed cycles with single embryo transfer, poor embryo quality would result in a significantly higher risk of LBW, regardless of cleavage-stage or blastocyst embryo transfer. Meanwhile, the transfer of poor cleavage-stage embryo was also associated with an increased incidence of PTB.
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