Preconception levothyroxine does not improve cognitive outcomes in children

Preconception treatment with levothyroxine fails to bring significantly better cognitive outcomes in children up to age 2 years compared with treatment initiated at 8–14 weeks of gestation, a study has found.

The authors performed this prospective, single-centre cohort study at a tertiary-care hospital to assess children’s cognitive function and ascertain the impact of preconception maternal hypothyroidism treatment on foetal neurodevelopment.

Overall, 466 women were assigned to either before conception (BC; n=187) or after conception (AC; n=279; 8–14 gestational weeks) groups by time point of hypothyroidism diagnosis and treatment. Levothyroxine therapy was adjusted based on the results of a monthly thyroid function test.

Neurocognitive development of children at age 6, 12, and 24 months was evaluated using the Gesell Development Diagnosis Scale (GDDS; Chinese version), with total score as the primary outcome.

Both BC and AC groups were similar at baseline antenatal visit, except for a higher proportion of thyroid peroxidase (TPO) antibody-positive participants in the former (p<0.001).

The GDDA neurodevelopmental assessment did not show any significant differences between groups at age 6, 12, and 24 months (p>0.05). However, there were slightly lower motor ability (p=0.009) and total (p=0.026) scores at 12 months and adaptability at 24 months (p=0.037) in the BC group.

On subgroup analysis for subclinical hypothyroidism, differences for motor ability (p<0.001) and total score (p=0.026) persisted with no significant differences in pregnancy and neonatal outcomes by severity and TPO status (p>0.05).