Longitudinal Assessment of Maternal Endothelial Function and Markers of Inflammation and Placental Function throughout Pregnancy in Lean and Obese Mothers
Authors: Stewart Frances M. , Freeman Dilys J. , Ramsay Jane E. , Greer Ian A. , Caslake Muriel , Ferrell William R. 
Published: December 2006

Background: Obesity in pregnancy is increasing and is a risk factor for metabolic pathology such as preeclampsia. In the nonpregnant, obesity is associated with dyslipidemia, vascular dysfunction, and low-grade chronic inflammation.

Aim: Our aim was to measure microvascular endothelial function in lean and obese pregnant women at intervals throughout their pregnancies and at 4 months after delivery. Plasma markers of endothelial function, inflammation, and placental function and their association with microvascular function were also assessed.

Methods: Women in the 1st trimester of pregnancy were recruited, 30 with a body mass index (BMI) less than 30 kg/m2 and 30 with a BMI more than or equal to 30 kg/m2 matched for age, parity, and smoking status. In vivo endothelial-dependent and -independent microvascular function was measured using laser Doppler imaging in the 1st, 2nd, and 3rd trimesters of pregnancy and at 4 months postnatal. Plasma markers of endothelial activation [soluble intercellular cell adhesion molecule-1 (sVCAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), von Willebrand factor (vWF), and plasminogen activator inhibitor (PAI)-1], inflammation (IL-6, TNFα, C-reactive protein, and IL-10), and placental function (PAI-1/PAI-2 ratio) were also assessed at each time point.

Results: The pattern of improving endothelial function during pregnancy was the same for lean and obese, but endothelial-dependent vasodilation was significantly lower (P &lt; 0.05) in the obese women at each trimester (51, 41, and 39%, respectively). In the postpartum period, the improvement in endothelial-dependent vasodilation persisted in the lean women but declined to near 1st trimester levels in the obese (lean/obese difference, 115%; P &lt; 0.01). There was a small but significant difference in endothelial-independent vasodilation between the two groups, lean response being greater than obese (P = 0.021), and response declined in both groups in the postpartum period. In multivariate analysis, time of sampling had the most impact on endothelial-independent function [18.5% (adjusted sum of squares expressed as a percentage of total means squared), P &lt; 0.001 for sodium nitroprusside response; 9.8%, P &lt; 0.001 for acetylcholine response], and obesity had the most impact on endothelial-dependent microvascular function (1.7%, P = 0.046 for sodium nitroprusside response; 19.3%, P &lt; 0.001 for acetylcholine response). Time of sampling (11.2%, P &lt; 0.001), IL-6 (4.0%, P = 0.002), and IL-10 (2.4%, P = 0.018) were significant independent contributors to variation in endothelial-dependent microvascular function. When obesity was entered into the model, the association with IL-6 and IL-10 was no longer significant, and obesity explained 6.8% (P &lt; 0.001) of the variability in endothelial-dependent microvascular function. In the 1st trimester, obese women had a significantly higher PAI-1/PAI-2 ratio [obese median (interquartile range), 0.87 (0.54–1.21) vs. lean 0.30 (0.21–0.47), P &lt; 0.001), reflecting the lower PAI-2 levels in obese pregnant women. In a multivariate analysis, 1st trimester BMI (7.6%, P = 0.012), IL-10 (8.2%, P &lt; 0.001), and sVCAM-1 (0.73%, P = 0.007) contributed to the 1st trimester PAI-1/PAI-2 ratio.

Conclusion: Obese mothers have a lower endothelium-dependent and -independent vasodilation when compared with lean counterparts. There was a higher PAI-1/ PAI-2 ratio in the 1st trimester in obese women, which improved later in pregnancy. Obese pregnancy is associated with chronic preexisting endothelial activation and impairment of endothelial function secondary to increased production of inflammatory T-helper cells-2 cytokines.