Thyroid antibody positivity in the first trimester of pregnancy is associated with negative pregnancy outcomes.

CONTEXT: Thyroid antibody positivity during pregnancy has been associated with adverse outcomes including spontaneous miscarriage, recurrent miscarriage, and preterm delivery.

OBJECTIVE: The objective of the study was to determine whether thyroid antibody positivity in the first trimester of pregnancy in euthyroid women was associated with maternal and neonatal adverse outcomes.

DESIGN: The present trial is a component of a prospective trial published in 2010 that evaluated screening for thyroid disease during pregnancy and the impact of levothyroxine therapy in women who were thyroid peroxidase positive with a TSH above 2.5 mIU/liter. The present study compared 14 maternal and neonatal adverse outcomes in 245 women who were euthyroid (TSH < 2.5 mIU/liter) and thyroid peroxidase positive in the first trimester to 3348 women who were euthyroid and thyroid peroxidase negative in the first trimester.

SETTING: The study was conducted in southern Italy at the ambulatory clinics of two community hospitals.

PATIENTS: The study consisted of 3593 women.

INTERVENTION: There was no intervention.

MAIN OUTCOME MEASURES: The main outcome measures were 14 maternal and neonatal complications.

RESULTS: The main result was an increase in very preterm delivery (<34 wk gestation at delivery) [4.5 vs. 1.8%; χ(2)(df = 1) = 8.58; P = 0.003] and respiratory distress [3.3 vs. 1.2%; χ(2)(df = 1) = 7.80; P = 0.005] in women who were thyroid antibody positive.

CONCLUSIONS: The present study provides further evidence of an association between thyroid antibody positivity and very preterm delivery in euthyroid women. The association with respiratory distress should be considered preliminary and awaits further study.