Abstract
OBJECTIVE: To determine normative values for heart rate patterns in healthy fetuses. METHODS: This research is from the Safe Passage Study conducted by the Prenatal Alcohol and SIDS and Stillbirth (PASS) Network. A standardized protocol assessed fetal heart rate (FHR), heart rate variability (HRV), and movement from 1655 fetuses at three-time points during gestation (20-24 weeks, 28-32 weeks, 34-38 weeks gestation). RESULTS: FHR decreased while HRV increased over gestation. At the latter two ages, males had significantly lower FHR than females while there were no sex differences in FHR at 20-24 weeks. When accounting for the fetal state during late gestation (34-28 weeks), we found that males had significantly lower FHR than females in the active fetal state only. CONCLUSION: Results demonstrate significant state, gestational age, and sex-related changes in cardiac activity, somatic activity, and autonomic function as the fetus approaches birth.