Antenatal Thyroid Screening and Childhood Cognitive Function

Le résumé fourni par la source

Previous studies have reported an association between reduced thyroid function during pregnancy and impaired cognitive development in offspring. This finding suggests that antenatal screening and treatment of thyroid deficiency could be beneficial. However, routine antenatal screening for hypothyroidism in pregnant women is not recommended. This randomized controlled trial was designed to determine whether antenatal screening and treatment of thyroid deficiency before 20 weeks of gestation was associated with improved cognitive function of offspring at 3 years of age. All participants were pregnant women older than 18 years at a gestational age of less than 15 weeks 6 days with no known thyroid disease before antenatal screening. Before randomization, all participants had reduced thyroid function defined as a high thyrotropin level or a low free thyroxine (T4) level. Cognitive function was compared in the offspring of women treated for thyroid deficiency early in pregnancy (screening and treatment group) and children of women who were untreated (control group). Blood samples were obtained at a gestational age of ≤15 weeks 6 days for measurement of thyrotropin and free T4 levels. The measurements were performed immediately after collection of samples in the screened/treated group, whereas samples obtained from the control group women were stored, and measurements were performed shortly after delivery. A positive screening result was considered to be serum thyrotropin levels above the 97.5th percentile, free T4 levels below the 2.5th percentile, or both. Patients in the screened/treated group with positive results received levothyroxine at a dose of 150 μg/d. The intelligence quotient (IQ) at 3 years of age in children was measured by psychologists blinded to the group assignments. Similar proportions of women in the screening group (5%) and control group (4.6%) were classified as having positive results based on a high thyrotropin level or a low free T4 level. At the start of levothyroxine treatment, the median gestational age was 13 weeks 3 days; treatment was adjusted as necessary to achieve a target thyrotropin level of 0.1 to 1.0 mIU/L. There was no significant difference between the mean IQ scores of children at 3 years of age born to treated women and untreated women with reduced thyroid function (IQ: 99.2 in the screening group and 100.0 in the control group); the difference was 0.8 IQ points; with a 95% confidence interval of −1.1 to 2.6 (P = 0.40 with intention-to-treat analysis). An IQ of less than 85 was found in 12.1% in the screened/treated group and 14.1% in the control group (difference, 2.1% [95% confidence interval, −2.6 to 6.7; P = 0.39]). Similar results were found in analyses limited to the women who adhered to treatment. These findings show that routine antenatal thyroid screening of pregnant women and treatment of those early in pregnancy who had reduced thyroid function does not improve cognitive function in their children at 3 years of age.

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