Maternal cardiometabolic dysfunction and fetal sex-specific alterations to uterine vascular reactivity in an ovine model of obesity during pregnancy.

Obesity during pregnancy is at pandemic proportions and predisposes women to pre- and postnatal cardiovascular dysfunction. The mechanisms underlying this maternal cardiovascular vulnerability remain unclear, partly due to a lack of translatable models capable of longitudinal in vivo cardiovascular monitoring. Here, we characterize a novel ovine model of maternal diet-induced obesity during pregnancy. Ewes were fed a control (CON) or obesogenic (OB; ad libitum concentrates) diet for 60 days pre-pregnancy and throughout gestation. Pregnant ewes were surgically instrumented with vascular catheters and Transonic flow probes using the wireless CamDAS system, which measured maternal cardiovascular function near term in free-moving ewes. Uterine artery vasoreactivity was assessed ex vivo by in vitro wire myography. OB ewes entered pregnancy 30% heavier than controls (P < 0.003) and were hyperglycaemic, hyperinsulinaemic and hyperlipidaemic during pregnancy, relative to CON ewes (all P < 0.05). OB ewes had elevated haematocrit and haemoglobin across pregnancy, and were hypertensive near term, with an increase in basal femoral artery blood flow, and elevated peripheral oxygen and glucose delivery (all P < 0.05). OB mothers carrying a female fetus showed increased uterine artery vascular resistance in vivo (P < 0.005) and reduced smooth muscle-dependent vasorelaxation ex vivo (P < 0.05) relative to CON. Conversely, OB mothers carrying a male fetus showed greater NO-independent mechanisms mediating the uterine vasodilator response to methacholine ex vivo (P < 0.001). Collectively, this study characterizes a robust model of maternal obesity during pregnancy that offers clinical translational potential and highlights fetal sex-specific changes to uterine artery function. KEY POINTS: Obesity during pregnancy is increasingly common and predisposes women to cardiovascular dysfunction during pregnancy and long after birth, but the specific mechanisms underlying this remain unclear. We developed a novel ovine model of diet-induced obesity during pregnancy that displays maternal hypertension, elevated haemoglobin, metabolic dysfunction, and alterations in uterine and peripheral blood flow and nutrient delivery near term. Mothers with obesity carrying a female fetus had elevated uterine vascular resistance in vivo and reduced uterine artery smooth muscle-dependent vasodilator reactivity ex vivo. Mothers with obesity carrying a male fetus showed no effect on uterine vascular resistance in vivo, but greater NO-independent mechanisms mediating the uterine vasodilator response to methacholine ex vivo. These findings highlight that fetal sex may influence maternal cardiovascular function during obese pregnancy.