Effects of different embryo culture media on birthweight following assisted reproductive technology.

Study questionDoes the type of embryo culture medium affect the birthweight of newborns conceived by ART?Summary answerAfter fresh embryo transfers, singleton newborns in the G5 and HTF groups exhibited higher birthweight z-scores and increased risks of being large for gestational age (LGA) compared to those in the Cook group.What is known alreadyCurrent studies have not yet determined whether embryo culture medium affects birthweight and, if such an effect does exist, the significance of embryo culture medium among all the influencing factors is not yet clear.Study design size durationA retrospective cohort study including 23 403 fresh ET cycles between 1 January 2010 and 31 December 2022 at the reproductive medical center of a university-affiliated hospital was conducted.Participants/materials setting methodsWe performed a retrospective cohort study including 23 403 fresh ET cycles. Four embryo culture media were analyzed: Cook, G5-PLUS, G5, and HTF. Multiple linear regression analysis was used to evaluate potential associations between embryo culture medium and birthweight z-score. Logistic regression analysis was used to evaluate potential associations between embryo culture medium and the risk of LGA and macrosomia. Random forest models were constructed to conduct significance analysis of all factors that may affect birthweight z-score.Main results and the role of chanceThe cohort comprised 4453, 8460, 7463, and 3027 singletons in the Cook, G5-PLUS, G5, and HTF groups, respectively. Compared to the Cook group, newborns in the G5 and HTF groups had higher birthweight z-scores (increased by 0.069 units, P < 0.001, and 0.073 units, P = 0.002, respectively) and higher risks of LGA (OR: 1.25, 95% CI: 1.12-1.39, P < 0.001; OR: 1.20, 95% CI: 1.05-1.37, P = 0.009, respectively), while newborns in the G5 group also had a higher risk of macrosomia (OR: 1.21, 95% CI: 1.06-1.39, P = 0.006). Of the main factors influencing birthweight, the embryo culture medium had a moderate significance.Limitations reasons for cautionDue to commercial and regulatory reasons, various culture media were used for different periods, thus resulting in the different number of cases for the four culture media groups.Wider implications of the findingsOur analysis revealed that the type of embryo culture medium directly affected birthweight z-scores and the risk of LGA and macrosomia in newborns conceived by ART. Consequently, the selection of embryo culture medium should be made cautiously. In addition, there's also a need for more post-market data on culture media for embryology labs.Study funding/competing interestsThis study was supported by National Key Research and Development Program of China (2023YFC2705604 and 2024YFC2706900) and the National Natural Science Foundation of China (82071721, 82371706, and 82288102). All authors have no conflicts of interest to report.Trial registration numberN/A.