Obstetric and perinatal outcomes in singleton pregnancies resulting from the transfer of blastocyst-stage versus cleavage-stage embryos generated through in vitro fertilization treatment: a systematic review and meta-analysis

Objective: To perform a systematic review and meta-analysis of obstetric and perinatal complications in singleton pregnancies after the transfer of blastocyst-stage and cleavage-stage embryos generated through IVF. Design: Systematic review. Setting: University hospital. Patient(s): Singleton pregnancies resulting from ET at the blastocyst stage versus those at the cleavage stage. Intervention(s): Medline, EMBASE, Cochrane Central Register of Clinical Trials DARE, and CINAHL (1980-2013) were searched. Two independent reviewers extracted data and assessed the methodological quality of the relevant studies using CASP scoring. Risk ratios and risk differences were calculated in Rev Man 5.1. Main Outcome Measure(s): Very preterm birth, preterm birth, small for gestational age, low birth weight, very low birth weight, congenital anomalies, perinatal mortality, preeclampsia, and placenta previa. Result(s): In vitro fertilization pregnancies occurring as a result of ET at the blastocyst stage were associated with a higher relative risk (RR; 95% confidence interval [CI]) of preterm (RR 1.27; 95% CI 1.22-1.31) and very preterm delivery (RR 1.22; 95% CI 1.10-1.35) in comparison with those resulting from the transfer of cleavage-stage embryos. The risk of growth restriction was lower in babies conceived through blastocyst transfer (RR 0.82; 95% CI 0.77-0.88). Conclusion(s): Data from observational studies show that ET at the blastocyst stage is associated with a higher risk of very preterm delivery. However, we were not able to adjust for confounders. Perinatal outcome data from existing randomized trials are needed to determine the safety of ET at the blastocyst stage compared with the cleavage stage. (Fertil Steril (R) 2013;100:1615-21. (C)2013 by American Society for Reproductive Medicine.)