Obstetric and perinatal outcomes after embryos cultured in one-step versus sequential culture media systems in vitrified–warmed single blastocyst transfer cycles

Research question: Does type of culture medium used influence obstetric and perinatal outcomes after vitrified-warmed single blastocyst transfers?Research question: Does type of culture medium used influence obstetric and perinatal outcomes after vitrified-warmed single blastocyst transfers?Design: Retrospective cohort study involving singletons after vitrified-warmed single blastocyst embryo transfers, using embryos cultured in either Irvine Continuous Single Culture medium (CSC) or Vitrolife G5 (TM) PLUS medium culture system between 2013 and 2020.Results: A total of 2475 women who had singleton deliveries were included for final analysis: 1478 had embryos cultured in CSC and 997 had embryos cultured in G5 (TM) PLUS medium. Birth outcomes, including preterm birth, mean birth weight, gestational age- and sex-adjusted birth weight (Z-scores), rates of large-for-gestational-age, small-for-gestational-age, low birth weight and macrosomia, and the distribution of newborn gender did not differ significantly between groups in crude and adjusted analyses. Women whose embryos were cultured in G5 (TM) PLUS frequently suffered from pregnancy-induced hypertensive disorders compared with those who had embryos cultured in CSC (4.7% versus 3.0%; P = 0.031). This difference was no longer significant after adjusting for several key confounders (adjusted odds ratio 1.49, 95% CI 0.94 to 2.38, P = 0.087). Other obstetric complications, including gestational diabetes mellitus, preterm premature rupture of membranes, abnormal placentation, postpartum haemorrhage and the mode of delivery were all similar between the two groups.Conclusions: The present study adds new information to the current evidence by suggesting that the embryo culture medium does not affect birth outcomes and obstetric complications when comparison is limited to Irvine CSC and Vitrolife G5 (TM) PLUS in vitrified-warmed single blastocyst transfer cycles.