Birthweight and placental weight; do changes in culture media used for IVF matter? Comparisons with spontaneous pregnancies in the corresponding time periods

STUDY QUESTION Have changes in culture media used for IVF resulted in changes in offspring birthweight or placental weight that differed from the trends in offspring from spontaneous conceptions during the corresponding time periods? SUMMARY ANSWER Changes in culture media used for IVF were associated with significant differences in offspring birthweight and in placental weight to birthweight ratio when compared with the trend in offspring from spontaneous conceptions during the time periods. WHAT IS KNOWN ALREADY The effect of culture media used for IVF on offspring birthweight has varied between studies. There is a large variation in birthweight between newborns, and birthweight may vary across populations and over time. Such variations may therefore have influenced previous results. STUDY DESIGN, SIZE, DURATION We included all singleton births from IVF at one treatment center in Norway during the years 1999–2011(n = 2435) and all singleton births from spontaneous conceptions in Norway during the same years (n = 698 359). PARTICIPANTS/MATERIALS, SETTING, METHODS Three different media were used for embryo culture; Medicult Universal IVF (1999 through 2007, n = 1584), Medicult ISM1 (2008 until 20 September 2009, n = 402) and Vitrolife G-1 PLUS (21 September 2009 through 2011, n = 449). We estimated mean birthweight and placental weight in IVF pregnancies by culture media. We also estimated mean weights in IVF and in spontaneous pregnancies by year of birth. Thereafter, we studied whether the changes in mean weights in IVF pregnancies differed from the changes in weight in spontaneous pregnancies in the periods corresponding to culture media changes by applying a grouped difference-in-difference analysis. Adjustments were made for parity, maternal age and gestational age at birth. MAIN RESULTS AND THE ROLE OF CHANCE In singleton offspring from IVF the mean birthweight was 3447.6 g with Medicult Universal, 3351.7 g with Medicult ISM1 and 3441.4 g with Vitrolife G-1 PLUS (P < 0.05). The corresponding mean placental weights were 684.1, 693.4 and 704.3 g (P < 0.05). In offspring from spontaneous conceptions the mean birthweight decreased (56.9 g) and the placental weight increased (9.3 g) during the study period. The adjusted difference in birthweight in offspring from IVF decreased with 35.0 g by the change from Medicult Universal to Medicult ISM1 (P = 0.16) and increased with 79.9 g by the change from Medicult ISM1 to Vitrolife G-1 PLUS (P = 0.01) when compar