Delayed rhythm formation of normal-structured, growth-restricted fetuses using fetal heart rate monitoring patterns.

AIMS Growth-restricted fetuses have delayed rhythm formation in utero. The awake-sleep cycle of fetal heart rate pattern is thought to represent fetal rhythm. We aimed to study if the emergence of rhythm formation on fetal heart rate pattern delays in fetal growth restriction compared to appropriate-for-date fetuses. METHODS This was a retrospective cohort study including 75, normal-structured, singleton fetuses. Of them, 21 were fetal growth restriction and the remaining 54 were appropriate-for-date infants. We examined timing of emergence of rhythm formation on fetal heart rate pattern comparing between fetal growth restriction and appropriate-for-date fetuses after adjusting possible confounding factors as outcome measures. RESULTS Rhythm formation was significantly delayed in fetal growth restriction (<10th percentile) compared to the appropriate-for-date subgroups (10-30, 30-50, 50-70 and 70-90th percentile) by 1-2 weeks. After adjusting confounding factors, growth restriction was the only independent variable to delay fetal rhythm formation. One infant for each group had neurodevelopmental disorder and the incidence did not reach statistically significant. CONCLUSION Based on fetal heart rate pattern analysis, growth-restricted fetuses show 1-2 weeks delay in rhythm formation compared to appropriate-for-date fetuses.