Is there a differential impact of parity on factors regulating maternal peripheral resistance?

Parity may influence cardiovascular adaptations during pregnancy. However, little is known about the influence of parity on maternal hemodynamic adaptations. In this prospective study, we investigated factors regulating peripheral resistance that control hemodynamic adaptations in pregnant women and evaluated differences in these factors between nulliparous and multiparous women. We evaluated 127 patients (nulliparous: 78, multiparous: 49) without any complications and not taking medications and assessed hemodynamics, arterial stiffness, modified flow-mediated dilation (mFMD) and heart rate variability, including power spectral and detrended fluctuation analysis (DFA). Diastolic blood pressure (BP) was significantly higher in nulliparous than multiparous women throughout pregnancy (P<0.05). Diastolic BP was significantly higher in nulliparous than multiparous women in the third trimester (95% confidence interval (CI), 2.43-9.73). A significant difference in high-frequency power was observed between nulliparous and multiparous (P<0.05) women, and was significantly lower in multiparous than nulliparous women in the third trimester (95% CI, 0.74-0.34). The low-frequency/high-frequency ratio was significantly increased in both groups between the first trimester and the third trimester (P<0.05). The DFA value, α2, significantly differed between nulliparous and multiparous (P<0.05), and was significantly lower in nulliparous than multiparous women (95% CI, -0.30 to -0.10). The mFMD and arterial stiffness remained approximately the same for nulliparous and multiparous women for all trimesters. Our results suggested that nulliparous women were characterized by greater autonomic nervous activity than were multiparous women.