Prediction of maternal and neonatal adverse outcomes in pregnant women treated for hypothyroidism

OBJECTIVE: To examine whether the concentrations of maternal serum TSH and free thyroxine (fT(4)) through pregnancy, the presence of thyroid autoimmunity (TAI) or the dose of levo-thyroxine (LT4) replacement can predict the occurrence of maternal or fetal/neonatal complications in pregnant women treated for maternal hypothyroidism. DESIGN: The study included 92 women with singleton pregnancies and primary hypothyroidism on LT4 replacement. Maternal serum TSH, fT(4), thyroid auto-antibodies and doses of LT4 were monitored throughout pregnancy. All maternal and fetal/neonatal complications were recorded. RESULTS: The overall prevalence of maternal and neonatal complications was 24.1%. Neither maternal TSH/fT(4) concentrations, presence of TAI nor dose of LT4 could predict the occurrence of complications. Pre-pregnancy body mass index (BMI) was higher in women who developed maternal complications [odds ratio (OR) 1.3, 95% confidence interval (CI) 1.1-1.5, p=0.007) and gestational week at delivery was lower in pregnancies complicated by neonatal (OR 0.5, 95% CI 0.3-0.8, p=0.001) or any type of complications (OR 0.6, 95% CI 0.4-0.9, p=0.008). CONCLUSIONS: The occurrence of maternal or fetal/neonatal complications in pregnant women treated for hypothyroidism cannot be predicted by maternal TSH/fT4 through pregnancy, presence of TAI or dose of LT4 replacement.