Elective single embryo transfer and perinatal outcomes: a systematic review and meta-analysis

Objective: To determine whether elective single embryo transfer (eSET) lowers the risk of poor perinatal outcomes associated with IVF, when [1] compared with double embryo transfer (DET) or multiple embryo transfer (MET), and separately, [2] compared with spontaneous conceptions.

Design: Systematic review and meta-analysis.

Setting: Centers for reproductive care.

Patient(s): Infertility patients.

Intervention(s): MEDLINE, Embase, and bibliographies were searched for the period 1978-2011. Two reviewers independently assessed titles, abstracts, and full studies, extracted data, and assessed quality. Dichotomous data were pooled using relative risks and continuous data with mean differences using a random effects model. Randomized controlled trials (RCTs), case-control studies, and cohort studies that examined any of the primary or secondary outcomes in singleton, twin, or multiple-order infants conceived by eSET as compared with [1] those conceived by DET or MET or [2] spontaneously conceived singleton gestations were included.

Main outcome measure(s): Primary outcomes were preterm birth (PTB, <37 weeks' gestation) and low birth weight (LBW, <2,500 g).

Result(s): Sixteen studies were included (eight RCTs, eight cohort studies). Compared with DET-conceived infants, eSET-conceived singletons were less likely to be born either preterm (RCT-based relative risk [RR] 0.37, 95% confidence interval [CI] 0.25-0.55) or with LBW (RCT-based RR 0.25, 95% CI 0.15-0.45; cohort study RR 0.51, 95% CI 0.29-0.91). However, compared with spontaneously conceived singletons, eSET gestations had higher risks of PTB (RR 2.13, 95% CI 1.26-3.61), placenta previa (RR 6.02, 95% CI 2.79-13.01), gestational diabetes (RR 1.69, 95% CI 1.19-2.42), and ectopic pregnancy (RR 6.40, 95% CI 4.38-9.35).

Conclusion(s): Elective single embryo transfer is associated with decreased risks of PTB and LBW compared with DET but higher risks of PTB compared with spontaneously conceived singletons.