Pregnancy associated with postpartum vascular changes

1. Mean arterial pressure at follow-up was lower among women who had become pregnant.

2. A greater decrease in arterial stiffness was observed among women who had become pregnant.

Evidence Rating Level: 2 (Good)

Study Rundown: Many physiologic changes occur during pregnancy in order to support the development of a growing fetus. Among these changes are cardiovascular adaptations, including an increase in cardiac output (CO) and blood volume and a decrease in peripheral vascular resistance and blood pressure. However, some women experience increases in blood pressure in pregnancy, which can be due to acute exacerbations of chronic hypertension or pregnancy complications like preeclampsia. Preeclampsia is defined as new onset hypertension after the 20^th week of gestation and either proteinuria or end organ dysfunction. Preeclampsia is less likely to occur in subsequent pregnancies compared to first pregnancies. It has been hypothesized that vascular changes during a prior pregnancy exert a protective effect against preeclampsia for a limited period of time. Past studies have shown that decreases in peripheral resistance persist after delivery and that mean arterial (MAP) pressure is lower in subsequent pregnancies. In the present work, the authors explored postpartum changes in cardiovascular physiology and found that MAP and arterial stiffness were reduced after pregnancy.

Strengths of the study included prospective design and measurement of multiple cardiovascular markers. Small sample size limited the statistical power of observed results such that associations may have gone undetected. Additionally, a single measurement of MAP at each time point may not account for natural fluctuations in blood pressure. Further evaluation of cardiovascular changes that happen during and after pregnancy are needed to better understand the mechanism by which preeclampsia risk is reduced for subsequent pregnancies.

Click to read the study in AJOG

Relevant Reading: Intolerance to volume expansion- a theorized mechanism for the development of preeclampsia

In-Depth [prospective cohort]: This study compared cardiovascular changes among women who became pregnant (n=17) and those who did not become pregnant (n=20) at baseline assessment and repeated again at matched elapsed time points (average of 30 months later). Outcomes of interest were MAP, CO, plasma volume, pulse wave velocity (PWV), uterine blood flow and flow-mediated vasodilation.

Women who became pregnant experienced a decrease in MAP that was not observed in the non-pregnant group (p=0.002). Women with an interval pregnancy also demonstrated a greater decrease in arterial stiffness as measured by pulse wave velocity when compared to non-pregnant women (p=0.005).

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