Embryo culture medium and neonatal birthweight

Study question: Does the type of medium used to culture fresh and frozen-thawed embryos influence neonatal birthweight after single embryo transfer (SET) in IVF? Summary answer: A comparison of two commercially available culture media showed no significant influence on mean birthweight and mean birthweight adjusted for gestational age, gender and parity (z-scores) of singletons born after a fresh or frozen-thawed SET. Furthermore, we show that embryo freezing and thawing may lead to a significantly higher mean birthweight. What is known and what this paper adds: Animal studies have shown that culture media constituents are responsible for changes in birthweight of offspring. In human IVF, there is still little knowledge of the effect of medium type on birthweight. Until now, only a small number of commercially available culture media have been investigated (Vitrolife, Cook® Medical and IVF online medium). Our study adds new information: it has a larger population of singleton births compared to the previously published studies, it includes outcomes of other media types (HTF and Sage®), not previously analysed, and it includes data on frozen-thawed SETs. Design: This study was a retrospective analysis of birthweights of singleton newborns after fresh (day 3) or frozen-thawed (day 5) SET cycles, using embryos cultured in either of two different types of commercially available culture media, between 2008 and 2011. Participants and setting: Before January 2009, a single-step culture medium was used: human tubal fluid (HTF) with 4 mg/ml human serum albumin (HSA). From January 2009 onwards, a commercially available sequential medium was introduced: Sage®, Quinn's advantage protein plus medium. Singletons born after a fresh SET (99 embryos cultured in HTF and 259 in Sage®) and singletons born after a frozen-thawed SET (32 embryos cultured in HTF only, 41 in HTF and Sage® and 86 in Sage® only) were analysed. Only patients using autologous gametes without the use of a gestational carrier were considered. Also excluded were: (vanishing) twins, triplets, babies with congenital or chromosomal abnormalities and babies born before 22 weeks of gestation. Main results and the role of chance: Analysis of 358 singletons born after a fresh SET and 159 singletons born after a frozen–thawed SET showed no significant difference between the HTF and Sage® groups in terms of birthweight. Gestational age, parity and gender of the baby were significantly related to birthweight in multiple linear regression analyses, and other possible confounding factors included maternal age, BMI and smoking, the number …