ESPE Abstracts

Background: The proper function of fetal thyroid gland depends on a proper content of iodine in mother’s diet and its transplacental transportation. Fetal iodine overload may be responsible for fetal hypothyroidism. Amiodarone is an iodine-rich antiarrhythmic medication and it contains 37% iodine by weight. Fetal tachyarrhythmia is associated with significant perinatal morbidity and mortality. If left untreated can cause congestive heart failure and non-immune hydrops fetalis. Transplacental therapy with oral antiarrhythmic drugs administered to the mother is usually effective in non-hydropic fetuses.

Aim: Report on long-term follow-up in child with neonatal hypothyroidism following transplacental amiodarone treatment for supraventricular tachyarrhythmia.

Results: During a routine newborn screening test elevated TSH was found (capillary TSH 18.29 mU/l from the first and TSH 19.23 mU/l from the second screening test) in a 9-day old girl. She was born at 40th week of gestation from spontaneous labor with Apgar scores of 10, weight 3520 g, length 53 cm from a young, healthy mother. At the 29th week of gestation it was stated that the fetal heart rate ranged from 230 to 250 beats per minute. The echocardiogram showed a structurally normal fetal heart, no hydrops fetalis was stated. Transplacental oral antiarrhythmic therapy to the mother with amiodarone was started and was continued up to 40th week. After birth the baby had sinus rhythm and did not require any treatment. At the presentation girl’s TSH was 20.1 mU/l, fT₄-10 pmol/l. Ultrasound revealed thyroid gland in typical position with normal echogenicity and volume of 0.7 ml. Treatment with L-thyroxine dose of 10 μg/kg per day was introduced. In the next 6 months the L- thyroxine therapy was adjusted with decreasing doses according to TSH and fT₄ evaluations. At the age of 7 months her thyroid hormone levels were normal and L- thyroxine therapy was stopped. The follow-up showed clinical and laboratory euthyreosis. At the age of five she presented a normal growth with the height in the 75th percentile and weight in the 50th percentile. Her mental and intellectual development was normal, and she met all appropriate developmental milestones.

Conclusions: Transplacental amiodarone treatment for supraventricular tachyarrhythmia may result in transient congenital hypothyroidism in newborns. Adequate treatment and precise monitoring of neurodevelopment in this children provide a possibility of good outcomes.