Received December 12, 2017
Accepted August 23, 2018

Objective: To evaluate if there are differences in the risks of obstetric outcomes in IVF/ICSI singleton pregnancies when compared fresh to frozen–thawed embryo transfers (FET). Methods: This was a systematic review and meta-analysis evaluating the obstetric outcomes in singleton pregnancies after FET and fresh embryo transfer. The outcomes included in this study were pregnancy-induced hypertension (PIH), pre-eclampsia, placenta previa, and placenta accreta. Result(s): The search yielded 654 articles, 6 of which met the inclusion criteria and reported on obstetric outcomes. When comparing pregnancies that arose from FET or fresh embryo transfer, there was an increase in the risk of obstetric complications in pregnancies resulting from FET when compared to those emerging from fresh embryo transfer in PIH (aOR 1.82; 95% CI 1.24–2.68), pre-eclampsia (aOR 1.32, 95% CI 1.07, 1.63), and placenta accreta (aOR 3.51, 95% CI 2.04–6.05). There were no significant differences in the risk between the FET and fresh embryo transfer groups when evaluating placenta previa (aOR 0.70; 95% CI 0.46–1.08). Conclusion(s): The obstetric outcomes observed in pregnancies arising from ART may differ among fresh and FET cycles. Thus, when evaluating to perform a fresh embryo transfer or a freeze-all cycle, these differences observed in obstetric outcomes between fresh and FET should be taken in account. The adverse obstetric outcomes after FET observed in this study emphasize that the freeze-all policy should not be offered for all the patients, but should be offered for those with a clear indication of the benefit of this strategy