Baroreceptor sensitivity and haemodynamics in normal pregnancy.
The objective of the study was to determine baroreceptor sensitivity and haemodynamics during the third trimester in normal pregnancy. The study group consisted of 20 primigravidae. The measurements were made at 28, 30, 32, 34, 36 and 38 weeks. The haemodynamic measurements were made by Doppler echocardiography and parameters calculated with standard formulae. Power spectral analysis was used to estimate the baroreceptor sensitivity in mid-frequency (MF) and high-frequency (HF) bands in msec/mmHg. Statistical tests performed were paired t-test and correlation coefficient. The mean baroreceptor sensitivity (BRS) in the mid-frequency band at 28, 30, 32, 34, 36 and 38 weeks were 5.19; 5.03; 5.52; 6.00; 6.77 and 7.82 msec/mmHg. The respective values for the high-frequency band were 7.52; 5.71; 7.99; 8.15; 8.53 and 10.87 msec/mmHg. The BRS in mid-high-frequency and high-frequency bands, mean arterial pressure and peripheral vascular resistance at 38 weeks of pregnancy were significantly higher than at 28 weeks, but the cardiac output was lower. A significant positive correlation of BRS with peripheral vascular resistance was observed. There was a significant negative correlation with cardiac output. The beneficial effects of increase BRS may lead to haemodynamic stability and stronger autonomic control of circulation. This may assist in maintaining a stable normal maternal blood pressure and a satisfactory placental perfusion during pregnancy. The absence of changes in BRS may be associated with pregnancy-induced hypertension and intrauterine growth restriction.
Jayawardana
M A
MA
Department of Obstetrics and Gynaecology, Faculty of Medical Sciences, University of Jayewardenepura, Nugegoda, Sri Lanka.