Psychomotor and audiological assessment of infants born to mothers with subclinical thyroid dysfunction in early pregnancy.

Background: To investigate the frequency and the effects of various degrees of maternal thyroid dysfunction in the first trimester of pregnancy, before the onset of fetal thyroid function, on psychomotor and audiological outcome of the offspring.

Methods: In a cohort of 691 pregnant women, undergoing thyroid screening between the 8th and 10th gestational week, eight were found to have a subclinical form of hypothyroidism and one was frankly hypothyroid. Treatment with L-thyroxine was started soon after diagnosis was made. Their nine offspring had a psychomotor and audiological assessment at the age of nine months. Psychomotor development was evaluated with the Brunet-Lèzine test, while audiological function was assessed with auditory brainstem responses (ABR's).

Results: Psychomotor developmental quotients were not different in patients and controls (99 +/- 6 vs 101 +/- 4). Regarding ABR pattern, there were no significant differences between patients and controls. Moreover, no correlation was found between maternal fT4 and psychomotor as well as audiological outcome in the offspring.

Conclusions: These findings are reassuring, since various degrees of maternal thyroid dysfunction in early pregnancy seem to have no adverse effects on the psychomotor and audiological outcome of the offspring up to nine months of age. A longer follow-up however is needed before definitive statements can be made.