Effect of maternal position and uterine activity on periodic maternal heart rate changes before elective cesarean section at term

INTRODUCTION: Because little is known about the effects of maternal position on periodic changes in the maternal heart rate (MHR) in late pregnancy, a prospective observational study was done at Tygerberg Academic Hospital in Cape Town. Pregnant women admitted for elective cesarean section were studied to determine the effect of changes in position on the maternal and fetal heart rates (FHR) and maternal blood pressure. MATERIAL AND METHODS: Continuous transabdominal non-invasive recording of MHR, FHR patterns and uterine activity was done for 1 h in 119 women, using the AN24 device from Monica Health Care. Maternal position was changed every 15 min from lateral to supine, then to the other lateral position and finally supine again. Blood pressure was measured in the left arm and left lower leg three times during each 15-min period. RESULTS: MHRs were four beats per minute slower in the left lateral position than in the right lateral position. Periodic MHR changes were seen in 13 (10.9%) women. Most of these (84.6%) were associated with uterine activity and not with maternal position. No changes in FHR patterns were observed after position changes. CONCLUSIONS: In a subgroup of pregnant women at term, uterine activity was associated with periodic decelerations of the MHR. In low risk pregnancies there seems to be no effect on the FHR pattern. Implications for the compromised fetus have not yet been investigated.