A LONGITUDINAL-STUDY OF MATERNAL HEMODYNAMICS DURING NORMAL-PREGNANCY

Objective: To investigate the maternal hemodynamic changes that occur during normal pregnancy. Methods: Serial hemodynamic investigations we re performed throughout normal pregnancy by thoracic electrical bioimp edance monitoring in 50 healthy women. Analysis of variance with repea ted measurements was used to evaluate the time course of a number of h emodynamic indices. Results: The mean heart rate (+/- standard error I SE]) increased gradually from 87 +/- 2 beats per minute at 10-18 weeks ' gestation to 92 +/- 1 beats per minute at 34-42 weeks' gestation. Me an arterial pressure decreased significantly U after 14 weeks' gestati on and increased significantly after 29 weeks' gestation During the th ird trimester, mean cardiac output and mean stroke volume decreased, a nd mean systemic vascular resistance increased significantly. The cour se of cardiac output during the third trimester was not uniform in all women; it increased in nine and decreased in 41 women. A significantl y higher mean cardiac output was found in nulliparous women compared w ith multiparous women (mean difference +/-SE 0.76 +/- 0.33 L/minute). The mean (+/-SE) cardiac output increased significantly from 6 (5.49 /- 0.16 L/minute) to 12 weeks' postpartum (5.91 +/- 0.19 L/minute). Co nclusion: Mean cardiac output and mean stroke volume decreased in late pregnancy. A significant difference in mean cardiac output was observ ed between nulliparous and multiparous women. Cardiac output usually, but not invariably, declined during the third trimester.