Background: Pregnancy requires substantial cardiovascular adaptation to support maternal–fetal health but also increases the risk of hypertensive disorders, preeclampsia, and fetal growth restriction. Routine vital signs do not assess stroke volume, cardiac output, or total peripheral vascular resistance. Non-invasive pulse-wave analysis using a computerized brachial cuff can measure these parameters, yet pregnancy-specific reference intervals are lacking.
Objective: To establish gestational age–specific reference intervals and z-score equations for key hemodynamic parameters between 10 and 39 weeks’ gestation and to evaluate the effect of maternal position.
Study design: In this prospective cross-sectional study, 300 pregnancies without hypertension, diabetes, fetal growth restriction, or incomplete data were analyzed. Hemodynamic measurements were obtained in the supine, left lateral, and sitting positions. Fractional polynomial regression using gestational age as the independent variable was used to derive means, standard deviations, percentiles, and z-scores. Positional differences were assessed using nonparametric tests.
Results: Heart rate increased from early pregnancy to the early third trimester and declined toward term. Stroke volume and stroke volume index decreased progressively across gestation. Cardiac output and cardiac index peaked at mid-gestation and declined near term. Total peripheral vascular resistance decreased through mid-pregnancy, reached a nadir in early third trimester, and increased at term. Compared with supine and sitting positions, the left lateral position was associated with lower brachial and central blood pressures, higher stroke volume, and lower vascular resistance, while cardiac output was similar across positions. Gestation-specific centiles and z-score equations were generated for all parameters.
Conclusion: This study establishes pregnancy-specific hemodynamic reference intervals using a computerized brachial cuff–based device. The observed gestational trends are consistent with prior studies and support left lateral positioning for hemodynamic assessment. These reference standards may facilitate improved cardiovascular risk assessment and individualized management in pregnancy.