INFANT BIRTH WEIGHT AND MATERNAL BMI: GENETIC VS EPIGENETIC CONTRIBUTIONS

Abstract

The prevalence of obesity is increasing worldwide. Obesity has been shown to have a negative effect on reproductive outcomes in both spontaneous and IVF pregnancies. Studies on the effect of maternal BMI on pregnancy success rates in donor oocyte IVF cycles are conflicting. Few studies have examined the effect of maternal BMI on neonatal outcomes. While increasing maternal BMI is associated with increased infant birth weight in both spontaneous and autologous IVF pregnancies, it is unclear whether this is primarily a genetic or epigenetic phenomenon. To our knowledge, this is the first study to examine the effect of donor BMI on infant birth weight in donor oocyte IVF cycles. The purpose of this study is to assess the relationship between infant birth weight and recipient and donor BMI in donor oocyte IVF cycles in order to determine the relative genetic (oocyte) and epigenetic (endometrial) contributions. IRB-approved retrospective cohort study. We conducted a retrospective cohort study of 130 donor oocyte IVF cycles resulting in a singleton live birth at a single IVF center from 2012-2018. Pearson correlation coefficients were calculated to examine the relationship between recipient and donor BMI and infant birth weight. ANOVA was conducted to compare infant weight among various BMI subgroups. Linear regression was used to adjust for the type of embryo transfer (fresh vs frozen), diabetes or gestational diabetes status, hypertension in pregnancy, gestational age, and infant sex. Recipients were >35 years of age on average and predominantly Caucasian. Decreased ovarian reserve was the most common etiology of infertility diagnosis. Forty-four percent of recipients were normal weight and 56% were overweight or obese. The mean age of oocyte donors was 26.7 ± 3.15 (Range 20-39) years. Seventy-eight percent of oocyte donors were normal weight and oocyte donors were predominantly Caucasian. There was no correlation between recipient BMI and infant birth weight (r=0; p=0.99). In contrast, there was a weakly positive, but non-significant, correlation between donor BMI and infant birth weight (r=0.02; p=0.76). This relationship persisted after adjusting for potential confounders. Several studies have shown a clear association between maternal BMI and infant birth weight in autologous IVF cycles. In this study we examined the relative contribution of donor and recipient BMIs to infant birth weight in donor oocyte IVF cycles. The lack of correlation observed between recipient BMI and infant birth weight along with the weak although not significant correlation between donor BMI and infant birth weight suggests that oocyte or genetic components may play a greater role in infant birth weight compared to epigenetic or endometrial factors. This study is limited by the relatively small sample size and lack of information on paternal BMI. Future studies aim to examine metabolic health outcomes in oocyte donor-conceived children.