Higher TSH levels in the first trimester of pregnancy are related to lower birth weight

To determine whether there was an association between birth weight and maternal thyroid function in the early first trimester. Early first trimester thyroid stimulating hormon (TSH) levels and birth weight percentiles of pregnants attending to our outpatient obstetrics clinic were searched retrospectively. Mothers of infants with small for gestational age (SGA) infants had statistically significantly higher mean TSH values when compared to mothers of infants with appropriate for gestational age (AGA) and large for gestational age (LGA) infants (2.5±8 and 1.7±1.5 respectively, p=0.007). Also, mothers of infants under 2500g weight had higher TSH values in the first trimester when compared to mothers of infants over 2500g weight (2±0.8 and 1.8±1.6 respectively, p=0.045). There was an association between high TSH levels in the early first trimester and low birth weight, screening of thyroid functions and treatment before pregnancy might be considered as a better policy.