[Influence of maternal hypothyroxinaemia during pregnancy on psychomotor development]

The maternal thyroid function during early pregnancy plays a fundamental role in foetal brain development as synthesis of thyroid hormone does not begin until the 20th week of gestation.

Throughout the year 2002, 147 women in their 37th week of pregnancy were enrolled for the study. To evaluate their thyroid function, the serum concentrations of free T4 and of TSH were determined. After birth, the psychomotor development of their children was evaluated with the Mc-Carthy scales.

The median value of free T4 was 9.37 pmol/l, being the data obtained from more than half of the sampled women below the hypothyroxinaemia threshold. Children born from mothers with T4 levels below percentile 10 showed a significantly lower score on the general cognitive index than those whose mothers had normal free T4 serum concentrations. A positive correlation was found between the values of maternal free T4 and the general cognitive index (r=0.43; p<0.01).

The concentrations of maternal free T4 are important, not only during the first months of pregnancy, but all along the process to ensure adequate development of the foetal brain.