Singleton babies conceived through assisted reproductive technology (ART) using fresh embryo transfer are more likely to experience preterm birth, being born small-for-gestational age, and having a low birthweight. Conversely, pregnancies resulting from frozen embryo transfer (FET) are associated with an increased risk of hypertensive disorders in pregnancy (HDP) and preeclampsia. Additionally, babies conceived through FET are more prone to being born large-for-gestational age and having a high birthweight. These distinctions have been affirmed through randomized controlled trials comparing obstetric outcomes between singletons born after elective FET and those born after fresh embryo transfer.

Primarily drawing from extensive cohort studies and meta-analyses, other maternal and obstetric outcomes, such as antepartum haemorrhage and perinatal mortality, appear to be similar in singleton pregnancies resulting from FET and fresh embryo transfer. However, when compared with naturally conceived (NC) pregnancies, ART singletons in general carries a higher risk of perinatal mortality.

There is substantial evidence indicating an elevated risk of HDP and the need for a caesarean section following programmed cycle (PC)-FET compared with natural cycle FET. Moreover, current evidence also suggests an increased likelihood of post-term birth, preeclampsia, postpartum haemorrhage, and high birthweight after PC-FET cycles. Caution should be taken when interpreting the potential health implications of epigenetic changes associated with FET, as there is still a lack of evidence regarding the functional consequences or altered health outcomes in adulthood. In pregnancies after oocyte donation (OD) the risk of preeclampsia, preterm birth and small-for-gestational age babies is increased. This may be due to a combination of primarily immunological factors and the PC-FET that is obligatory in most OD recipient cycles.