Abstract
ObjectiveTo 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).MethodsThis 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.ResultsThe search yielded 654 papers, 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 transfers 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).ConclusionThe 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 found in obstetric outcomes between fresh and FET should be taken into account. The adverse obstetric outcomes after FET found in this study emphasize that the freeze-all policy should not be offered to all the patients, but should be offered to those with a clear indication of the benefit of this strategy.
Highlights
Today, nearly one in six couples faces fertility issues, as they fail to achieve a clinical pregnancy even after regular copulation (Boivin et al, 2007; Zegers-Hochschild et al, 2009)
Births from singleton assisted reproductive technology (ART) pregnancies following frozen-thawed embryo transfers (FET) have been associated with high birth weights, there was a lower risk of preterm births when compared to fresh transfer cycles (Maheshwari et al, 2012; Spijkers et al, 2017; Wennerholm et al, 2013), a finding that highlights the impact of the clinical procedure itself, and not maternal characteristics, on these outcomes (Pinborg et al, 2014)
We found that the risk of developing pregnancy-induced hypertension (PIH) increased in the FET group compared to the fresh embryo transfer group (Figure 2a)
Summary
Nearly one in six couples faces fertility issues, as they fail to achieve a clinical pregnancy even after regular copulation (Boivin et al, 2007; Zegers-Hochschild et al, 2009). FET cultivates better environmental conditions within the uterus during embryo transfer, leading to improved endometrial receptivity (Barnhart, 2014; Weinerman & Mainigi, 2014) This better uterine environment may be related with better placentation during a FET cycle, leading to improved obstetric outcomes when compared to fresh transfer cycles (Maheshwari et al, 2012; Roque et al, 2015b; Shapiro et al, 2013). Births from singleton ART pregnancies following FET have been associated with high birth weights, there was a lower risk of preterm births when compared to fresh transfer cycles (Maheshwari et al, 2012; Spijkers et al, 2017; Wennerholm et al, 2013), a finding that highlights the impact of the clinical procedure itself, and not maternal characteristics, on these outcomes (Pinborg et al, 2014). Published meta-analysis comparing obstetric outcomes in pregnancies after fresh and FET did not report major obstetric outcomes such as pregnancy-induced hypertension (PIH), pre-eclampsia, placenta previa, and placenta accreta (Maheshwari et al, 2012; Pinborg et al, 2013)
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