Maternal thyroid hormones during pregnancy, childhood adiposity and cardiovascular risk factors: the Generation R Study

Objective Variation in maternal thyroid function during early pregnancy may permanently affect childhood growth and cardiovascular development. We examined the associations of early pregnancy maternal TSH and free T4 (FT4) levels with childhood growth, body composition and cardiovascular characteristics. Methods We performed a population-based prospective cohort study among 5646 mothers and their children. Maternal thyroid parameters were assessed in early pregnancy (median: 13.2 weeks; 95% range: 9.7-17.6 weeks). Childhood growth was repeatedly measured from birth to 6 years. At the age of 6 years, childhood body mass index (BMI), total body and abdominal fat distribution, blood pressure and left ventricular mass were measured. Results Maternal thyroid parameters were not consistently associated with childhood length and weight growth characteristics. Lower maternal TSH levels were associated with lower childhood BMI, total fat mass, abdominal subcutaneous fat mass area and diastolic blood pressure (P-values <0.05), but not with preperitoneal abdominal fat mass area, systolic blood pressure or left ventricular mass. Higher maternal FT4 levels were associated with lower childhood BMI, abdominal subcutaneous and preperitoneal fat mass area (P for trends <0.05), but not with other cardiovascular characteristics. Clinically maternal hypothyroid or hyperthyroid statuses were not associated with childhood growth, body fat or cardiovascular outcomes. Conclusions Maternal thyroid function during early pregnancy may influence childhood body composition and cardiovascular development. Further studies are needed to replicate these findings and to examine the influence of maternal thyroid hormone levels during pregnancy on long-term growth and cardiovascular development in the offspring.