Abstract
BackgroundExtended 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.ObjectivesTo compare obstetric and perinatal outcome using embryos vitrified on day 7 with those vitrified on day 3, day 5, and day 6.MethodsData were collected from 4489 infertile women who gave birth to live-born 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.ResultsAfter 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.ConclusionIn 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.
Highlights
Nowadays, in vitro fertilization (IVF) practice has presented a move toward blastocyst culture to achieve more favorable pregnancy outcomes compared to cleavage-stage embryo transfer (Glujovsky et al, 2016; Holden et al, 2018), especially since single embryo transfer policy has been advocating in many countries (Devine et al, 2015)
A total of 4489 vitrified-warmed cycles from women who meet the inclusion criteria were included after the transfer of day 3, day 5, day 6, and day 7 embryo transfer, and they were further subdivided into three matched group based upon propensity score matching (PSM) method to reach unbiased baseline characteristics (Figure 1)
Our results demonstrated that day 7 blastocysts were associated with higher Z-score and higher risks of VLGA compared with day 3 group, and we did not found any significant difference in the comparison between day 5, day 6, and day 7 group
Summary
In vitro fertilization (IVF) practice has presented a move toward blastocyst culture to achieve more favorable pregnancy outcomes compared to cleavage-stage embryo transfer (Glujovsky et al, 2016; Holden et al, 2018), especially since single embryo transfer policy has been advocating in many countries (Devine et al, 2015). Blastocyst culture is important for the selection of the most viable embryo for transfer, with regards to reducing the incidence of multiple pregnancies, which increases the adverse obstetric and perinatal outcomes. Existing data about the obstetric outcome and the safety for offspring resulting from the transfer of day 7 blastocysts is rare
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