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Elevated thyrotropin levels increase prematurity risk
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DENVER — The risk for prematurity in offspring is increased with maternal serum thyrotropin levels above the trimester-specific ranges during pregnancy, according to a presenter here.
“There is conflicting evidence in the current literature regarding the potential effects of maternal subclinical hypothyroidism on adverse pregnancy and perinatal outcomes,” Sun Y. Lee, MD, ECNU, instructor of medicine in the section of endocrinology, diabetes and nutrition at Boston University School of Medicine, told Endocrine Today. “Our study presents another evidence of potential association between maternal subclinical hypothyroidism in pregnancy and increased risk of prematurity, suggesting the need for more research in the area.”
Lee and colleagues evaluated data from electronic medical records on 6,100 pregnant women with a singleton gestation seen for prenatal care and their infants at Boston Medical Center between Jan. 1, 2007, and May 22, 2014.
Normal thyrotropin values were defined by trimester-specific ranges: 0.1 to 2.5 mIU/L in the first trimester, 0.2 to 3 mIU/L in the second trimester and 0.3 to 3 mIU/L in the third trimester.
Prematurity was defined as gestational age at birth less than 37 weeks, and low birth weight was defined as 2,500 g or less.
Mean gestational age at birth was 38.5 weeks, and mean birth weight was 3.2 kg.
Low thyrotropin measured during the first trimester was found in 63% of participants, and 6.3% of those had elevated trimester-specific thyrotropin values (median, 3.33 mIU/L).
After adjustment for potential confounders, elevations in serum thyrotropin levels during any trimester of pregnancy were associated with an increased risk for prematurity compared with normal thyrotropin values (OR = 1.52; 95% CI, 1.06-2.16).
Fetal loss, preterm labor, placental abruption, preeclampsia/eclampsia, cesarean section, gestational hypertension, gestation diabetes, neonatal respiratory distress syndrome, neonatal admission to the ICU or low birth weight were not predicted by elevated serum thyrotropin concentrations.
“Although there is no clear recommendation for thyroid function testing in pregnant women, it may be beneficial for the providers to be vigilant in assessing potential symptoms and risks for hypothyroidism in pregnant women,” Lee said.
Lee added that although the study included a large population, causality cannot be inferred since pre-existing medical records were analyzed.
“However, other prospective studies have shown similar results of increased prematurity risk, as well as increased risks of other adverse obstetric outcomes,” she said. “Given the ongoing debates over the need for universal screening of thyroid function in pregnant women, further research assessing the potential effects of maternal subclinical hypothyroidism on pregnancy outcomes in a more controlled manner would be needed.” – by Amber Cox
Reference:
Lee SY, et al. Oral 22. Presented at: 86th Annual Meeting of the American Thyroid Association; Sept. 21-25, Denver.
Disclosure: Lee reports no relevant financial disclosures.