We report a rare case of fetal goitrous hypothyroidism complicated by polyhydramnios and preterm labor in a mother without thyroid gland pathology. The diagnosis was made in the 26th week by ultrasound and cordocentesis [TSH 170 microU/ml, free T(4) 0.2 ng/dl]. The therapeutic regime required repeated fetal blood sampling for determination of thyroid hormones. Five intra-amniotic administrations of 250 microg levothyroxine (LT4) weekly were initiated. Because of the persisting goiter and the elevated level of TSH (128 microU/ml in 32 weeks) in the fetal serum the dosage had to be adjusted to 500 microg LT4 in the next five injections. TSH in fetal serum declined to 49.2 microU/ml in 36 weeks. Normal fetal growth and an uncomplicated course of pregnancy between the 27th and 37th week of gestation were observed. Monitoring of intrauterine therapy by determination of TSH in fetal serum may provide more reliable data than measuring TSH in amniotic fluid. A review of 15 cases of fetal goitrous hypothyroidism in the English literature is presented.
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