Fetal heart rate tracing patterns associated with congenital hypothyroidism

Objective: This study was undertaken to determine fetal heart rate (FHR) tracing patterns associated with congenital hypothyroidism. Study Design: FHR patterns of 59 women whose babies were diagnosed with congenital hypothyroidism were retrospectively compared with tracings of 78 of their siblings. Tracings were interpreted during the first stage of labor. Multivariable analysis was used to control for confounders. Results: Neonates with congenital hypothyroidism had significantly higher rates of reduced variability in FHR tracing patterns as compared with those without congenital hypothyroidism (49.2% vs 3.8%; odds ratio, 24.1; 95% confidence interval, 6.8-85.3; P < .001). No significant differences were noted between the groups regarding decelerations or baseline abnormalities. The significant association between congenital hypothyroidism and reduced variability persisted after controlling for confounders such as treatment with pethidine, MgSO4, and gestational age (odds ratio, 14.1; 95% confidence interval, 1.1-190.7; P = .046). Conclusion: Congenital hypothyroidism is significantly and independently associated with reduced variability in FHR tracing patterns.