Autonomic cardiovascular reflexes in pregnancy. A longitudinal study.

Cardiovascular reflexes were studied in 22 healthy women before they were pregnant, once during each pregnancy trimester and after delivery to evaluate the effect of pregnancy on autonomic control of haemodynamics. The Valsalva manoeuvre, the deep breathing test, the orthostatic test and the isometric handgrip test were used to assess changes in autonomic nervous function. We found that pregnancy altered the heart rate response in the Valsalva manoeuvre, the deep breathing test and the orthostatic tests. The deep breathing difference (p = 0.03) and max/min ratio (p = 0.03) decreased in pregnancy, whereas standing heart rate increased (p < 0.0001). Both the systolic and diastolic blood pressure increased after standing up during pregnancy. The circulatory responses to isometric exercise were not affected by pregnancy. The results show that parasympathetic responsiveness is decreased in pregnancy and that it returns to normal after delivery.