Maternal high BMI: Sex-dimorphic alterations in maternal and offspring stress indices

Maternal body mass index (BMI) influences pregnancy and birth outcomes along with child metabolic and neurodevelopmental health and fetal sex may be a moderating factor in these effects. Alternations in autonomic nervous system (ANS) functioning, identified in heart rate (HR) measurements, could present early markers of these prenatal programming effects in both the mother and the developing fetus. This study examines the associations between pre-pregnancy BMI and maternal and fetal ANS functioning and infant postnatal behavioral outcomes stratified by fetal sex. Pregnant women (N=176) were recruited at gestational week (GW) T1: 12-22 and categorized into Normal (BMI< 25) or High BMI (BMI > 25). Women attended laboratory sessions at T2: GW 23-28, and T3: GW 34-36 to assess maternal and fetal HR and HR variability (HRV) at baseline and after a stressor at T3. Infant behavior was assessed at 4 months using the Infant Behavior Questionnaire-Revised. Women with high BMI bearing female fetuses had higher HR and lower HRV at both gestational time points. Later in the third trimester, female fetuses of high BMI women exhibited lower HRV when challenged with a stressor. At 4 months, female infants were rated as having lower scores on the Orienting/Regulatory scale. Our findings provide evidence of female sex-specific programming of maternal pre-pregnancy BMI on maternal ANS regulation and neurodevelopment identified in-utero and continuing into early infancy.