Intrauterine treatment of thyroid goiters.

A fetal thyroid goiter detected by ultrasonography at 20 weeks of amenorrhea (WA) was diagnosed at 23 WA by a second ultrasound examination and a TSH assay in amniotic fluid. Since a sample of fetal blood at 27 WA showed that hypothyroidism was compensated and that goiter size and amniotic fluid volume were stable, intra-amniotic injection of 300 micrograms of L-thyroxine was delayed until 36 WA. This injection was performed before delivery to avoid potential perinatal complications (dystocia and neonatal respiratory distress) caused by large goiters.