Fetal
goiter was detected by routine ultrasound in early pregnancy, gestational week (GW) 18, in a 28-year-old woman with no thyroid history, normal
thyroid hormone levels and no
TSH receptor or
thyroid peroxidase antibodies. An umbilical cord blood sample was drawn in GW 23. The analysis indicated fetal
hypothyroidism with TSH >100 mU/l (reference value 6.8 ± 2.9, mean ± SD), fT4 3.8 pmol/l (reference value 16.5 ± 5.3, mean ± SD). Intra-amniotic
injections of
thyroxine were given in conjunction with ultrasound every 7-10 days, in total nine times during GW 24-33. A dose of 10 µg
thyroxine/kg of estimated
fetal weight per day was administered on six occasions, and 5 µg/kg/day the last three times. Upon
injections of
thyroxine further growth of the
goiter was reduced. Elevated amniotic TSH levels fell from 13 to 2.5 mU/l (reference range 0.04-0.51). Throughout pregnancy, fetal heart rate and skeletal maturation were within normal limits. In week 34,
chorioamnionitis was suspected and the child was delivered by
cesarean section. Cord blood revealed TSH 596 mU/l (reference value 8.0 ± 5.12, mean ± SD), fT4 4.4 pmol/l (reference value 19.3 ± 4.3, mean ± SD) and total T3 1.18 nmol/l (reference value 0.5 ± 0.3, mean ± SD); the newborn was put on
thyroxine supplementation. Psychomotor development of the child, now 3 years old, has been uneventful. The reported experience of treating dyshormonogenetic fetal
goiter is limited but growing, creating a need for guidelines on administration of intra-amniotic
thyroxine and monitoring treatment.