Subclinical Changes in Maternal Thyroid Function Parameters in Pregnancy and Fetal Growth.

ABSTRACT: Context:Overt thyroid disease in pregnancy is a known risk factor for abnormal fetal growth and development. Data on the effects of milder forms of variation in maternal thyroid function on intrauterine growth are less well examined. Objective:We explored these associations using repeated thyroid hormone and ultrasound measurements. Design, Setting, and Participants:Data were obtained from 439 pregnant women without diagnosed thyroid disease who were participants in a case-control study of preterm birth nested within an ongoing prospective birth cohort in Boston, Massachusetts. Main Outcome Measures:Ultrasound and delivery indices of fetal growth were standardized to those measured in a larger population. Results:At median 10, 18, and 26 weeks of gestation, we observed significant inverse associations between free thyroxine (FT4) and birth weight z scores, with the strongest association detected at median 10 weeks, at which time a 10% increase in FT4 was associated with a 0.02 z score decrease (?8.5 g) in birth weight (? = -0.41 for ln-transformed FT4; 95% confidence interval, -0.64 to -0.18). FT4 was also inversely associated with repeated measurements of estimated fetal weight, head circumference, and abdominal circumference. We observed weaker inverse associations for total T4 and a positive relationship between total triiodothyronine and birth weight z scores. We did not observe any associations for thyroid-stimulating hormone. Conclusion:In pregnant women without overt thyroid disease, subclinical changes in thyroid function parameters may influence fetal growth.

SUBMITTER: Johns LE 

PROVIDER: S-EPMC6018657 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature