Association and predictive accuracy of high TSH serum levels in first trimester and adverse pregnancy outcomes.

CONTEXT High serum levels of TSH have been associated with adverse pregnancy outcomes by some studies, and not by others. OBJECTIVE The aim of the study was to assess the association between high levels of TSH in the first trimester of pregnancy and adverse pregnancy outcomes; and to examine the predictive accuracy as a screening test. SETTING AND PARTICIPANTS Serum levels of TSH were measured in a cohort of 2801 women with a singleton pregnancy attending first trimester Down syndrome screening. Information on maternal and infant outcomes was obtained through record linkage to population-based birth and hospital data. Association between high TSH (>95th and >97.5th centiles) multiple of the median levels, and risk of adverse pregnancy outcomes was evaluated using multivariable logistic regression, and the predictive accuracy of models was assessed. MAIN OUTCOMES Rates of infants being small for gestational age (SGA), preterm birth, preeclampsia, miscarriage, and stillbirth were investigated. RESULTS High TSH multiple of the median levels were associated with SGA (<10th centile) [adjusted odds ratio (aOR), 1.71; 95% confidence interval (CI), 0.99-2.94]; preterm birth at less than 37 wk gestation (aOR, 2.59; 95% CI, 1.21-5.53); miscarriage (aOR, 3.66; 95% CI, 1.59-8.44); and a composite measure of any study outcome (aOR, 2.10; 95% CI, 1.23-3.59). The area under the receiver operator characteristic curves were 0.69 (95% CI, 0.65-0.73) for SGA; 0.56 (95% CI, 0.51-0.61) for preterm birth; 0.70 (95% CI, 0.61-0.79) for miscarriage; and 0.63 (95% CI, 0.60-0.65) for any adverse pregnancy outcome. CONCLUSIONS High TSH serum levels during the first trimester of pregnancy were associated with adverse pregnancy outcomes; however, the predictive accuracy was poor. Screening for high TSH levels in the first trimester would be of no benefit to identify women at risk.