Background: Excessive gestational weight gain (GWG) may cause maladaptive sympathetic neural responses and increase pregnancy risk, which may differ by maternal body mass index. We hypothesized that excessive GWG would further increase muscle sympathetic nerve activity across gestation, particularly in women with overweight or obesity.
Methods: Ninety pregnant women were studied longitudinally during early and late gestation and postpartum. Participants were classified by body mass index in early pregnancy and by GWG in late pregnancy based on the 2009 Institute of Medicine guidelines, forming 4 groups: normal-weight women with normal (n=17) or excessive GWG (n=26), and overweight/obese women with normal (n=16) or excessive GWG (n=31). Resting systolic and diastolic blood pressure, heart rate, and muscle sympathetic nerve activity were measured. Pregnancy outcomes were obtained from hospital maternity records, and complications were diagnosed according to established clinical criteria.
Results: Muscle sympathetic nerve activity increased across gestation and was greater in overweight/obese groups than in normal-weight groups (P=0.017), with no difference between excessive and normal GWG groups (P=0.845). Heart rate and systolic blood pressure increased from early to late pregnancy and were higher in overweight/obese groups, irrespective of GWG. Diastolic blood pressure increased most in normal-weight women with excessive GWG (P<0.05), reaching levels comparable to those in the overweight/obese groups. Among all groups, women with overweight/obesity and excessive GWG had the numerically highest complication rate.
Conclusions: The changes in muscle sympathetic nerve activity across gestation did not differ by GWG, even among women with overweight/obesity, suggesting that the increased risk from excessive GWG is unlikely to be mediated by sympathetic activity.
Keywords: blood pressure; body mass index; heart rate; muscles; pregnancy.