Maternal hemodynamics in normal pregnancy: reference ranges and role of maternal characteristics

ABSTRACT Objectives The main aim of this study was to construct reference ranges of maternal central hemodynamic parameters during pregnancy. The second aim was to determine the maternal and pregnancy characteristics that influence these hemodynamic parameters. Methods This was a prospective cohort study of low‐risk pregnant women attending for routine antenatal care at St George's Hospital, London, UK. Exclusion criteria included any medical disorder present at the time of study recruitment, or development of hypertension or intrauterine fetal growth restriction following study recruitment. Stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) were obtained using non‐invasive cardiac output monitoring (USCOM‐1A®). USCOM‐1A utilizes a non‐imaging probe in the suprasternal notch to obtain velocity‐time integrals of transaortic blood flow at the left ventricular outflow tract. Once the distribution of the data with respect to gestational age had been determined, maternal characteristics were added to the model to test whether they provided a significant improvement in the prediction of the median value. Results The study included 627 women with a singleton pregnancy. The estimated median CO was constant for a maternal age above 32 years, but was around 0.5 L/min higher for women aged ≤ 25 years (P