Effect of gestational age on baseline fetal heart rate during the third trimester of pregnancy

Analysis of the fetal heart rate in 3,127 reactive nonstress tests revealed that the baseline rate decreased significantly between 28 and 41 weeks' gestation (6.4 beats per minute [4.5%]). Analysis of 235 women with two tests at least four weeks apart revealed that while the majority (51.1%) demonstrated a decrease, 26.8% experienced a rise in the baseline rate during the testing interval.