A low plasma volume in formerly preeclamptic women predisposes to the recurrence of hypertensive complications in the next pregnancy.

Background: Formerly preeclamptic women with a subnormal plasma volume (PV) have an increased risk to develop a hypertensive disorder in a subsequent pregnancy as compared to women with normal PV. In the current study we tested the hypothesis that formerly preeclamptic women who develop recurrent disease in their next pregnancy differ from their counterparts with an uneventful next pregnancy by a lower pre-pregnant PV, a lower venous capacitance, smaller rises in these indices in early pregnancy, a lower renal adaptive response, and a lower response to mild exercise.

Patients and methods: We enrolled 33 formerly preeclamptic women in this study. Only 14 conceived within the study period, with seven of them developing a recurrent hypertensive disorder in their next pregnancy (RECUR), while seven had an uneventful next pregnancy (NORM). Before pregnancy and at 12 weeks of gestational age, we compared the following variables between these subgroups: PV, venous capacitance, effective renal plasma flow (ERPF), glomerular filtration rate (GFR), and the responses in stroke volume (SV) and heart rate (HR) to mild exercise. To estimate venous capacitance, we infused 500 mL of a modified gelatine solution in 30 minutes while recording the change in cardiac output (pulse contour analysis). The ratio of percent change in blood volume to percent change in cardiac output in response to a standardized small volume load provides an estimate for venous capacitance.

Results: RECUR differed from NORM by a 20% lower pre-pregnant PV (P <.02) and venous capacitance (0.29 [0.11-0.55] vs 0.86 [0.64-2.03] P = .002). NORM and RECUR were comparable with respect to pregnancy-induced rise in PV, renal hemodynamics and function, and response to mild exercise at 12 weeks. Newborn weight correlated positively with pre-pregnancy PV (R(2) = 0.53 and P = .04).

Conclusion: Formerly preeclamptic women with a recurrent hypertensive disorder in their next pregnancy differed from their counterparts with an uneventful next pregnancy by a lower pre-pregnant PV and a lower venous capacitance, the latter two indices correlating also inversely with the incidence of fetal growth restriction. The preserved acute response to volume-related stimuli in women with a low pre-pregnant PV supports the view that the predisposition of low pre-pregnant PV to adverse pregnancy outcome may result from a concomitant, PV-dependent change setpoint and/or gain in the stimulus/response interrelation of the volume regulatory system.