MATERNAL HYPOTHYROIDISM DURING EARLY-PREGNANCY AND INTELLECTUAL-DEVELOPMENT OF THE PROGENY

Objective: To investigate whether maternal hypothyroidism before the o nset of fetal thyroid function influences mental development of the of fspring. Design: We examined IQs in children in whom the mothers had b een hypothyroid during early pregnancy (group 1). The IQs were compare d with those of siblings who were not exposed to maternal hypothyroidi sm during gestation (group 2). Patients: Group 1 consisted of eight ch ildren. Mothers were examined for thyroid status during the fifth to 1 0th gestational weeks and were found to have distinctly low thyroxine levels and high thyrotropin levels; the levels became normal after thy roxine supplementation by 13 to 28 weeks of gestation. Seven of the ei ght children had nine siblings who had not been exposed to maternal hy pothyroidism during gestation (group 2). Ages at examination were 4 to 10 years in group 1 and 4 to 15 years in group 2. Results: All childr en in group 1 showed normal IQs. There was no significant difference i n the mean IQ between the children in group 1 who had siblings (112+/- 11) and their siblings in group 2 (106+/-8). Even the subject whose mo ther had had the lowest thyroxine level (free thyroxine, 2.3 pmol/L) h ad an IQ similar to that of his sibling. Conclusion: These data provid e evidence against. the presence of adverse effects of maternal hypoth yroidism during early pregnancy on the subsequent mental development o f the offspring.