Venous and autonomic function in formerly pre-eclamptic women and controls matched for body mass index

Objective Prepregnancy reduced plasma volume (PV) increases the risk of subsequent pre-eclamptic pregnancy. Reduced PV is thought to reflect venous reserve capacity, especially when venous vasculature is constricted and sympathetic tone is elevated. As obesity might affect these variables, and is associated with pre-eclampsia, increased body weight may underlie these observations. The aim of this study was to determine whether the relationship between reduced venous reserve and pre-eclampsia is independent of body mass index (BMI).

Methods This was an observational case-control study in which venous reserve capacity in 30 formerly pre-eclamptic, but currently non-pregnant, women divided equally into three groups based on BMI (BMI 19.5-24.9, 25.0-29.9 or >= 30.0 kg/m(2)), was compared with that in 30 healthy parous, non-pregnant controls. Cases and controls were matched for BMI, age and parity. Venous reserve capacity was quantified by assessing PV and venous compliance (VeC). The autonomic nervous system regulating venous capacitance was evaluated using heart rate (HR) variability analysis, with the women in a resting supine position and during positive head-up tilt (HUT).

Results Compared with controls, formerly pre-eclamptic women had, when in a resting supine position, lower PV (1339 +/- 79 vs 1547 +/- 139 mL/m2 (P<0.0001)), lower VeC (0.04 +/- 0.02 vs 0.07 +/- 0.02 mL/dL/mmHg (P<0.0001)), higher sympathetic tone (1.9 +/- 1.1 vs 1.2 +/- 0.7 (P= 0.002)) and lower baroreceptor sensitivity (BRS; 8.7 +/- 3.8 vs 19.0 +/- 1.7ms/mmHg (P<0.0001)). During HUT, women with a history of pre-eclampsia had less modulatory capacity over VeC and BRS, while HR and sympathetic tone remained consistently higher.

Conclusions Women with a history of pre-eclampsia had reduced venous reserve capacity compared with that in BMI-matched controls. This is reflected by lower PV and VeC, with the autonomic balance being shifted towards sympathetic dominance and lower BRS. This suggests that underlying reduced venous reserve, but not BMI, relates to pre- eclampsia. Copyright (c) 2018 ISUOG. Published by John Wiley & Sons Ltd.