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 (fT4) 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, fT4, 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/fT4 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.