Thyroid peroxidase antibody in women with unexplained recurrent miscarriage: prevalence, prognostic value, and response to empirical thyroxine therapy.

Objective: To determine the prevalence, prognostic value, and response to thyroxine therapy of thyroid peroxidase antibody (TPOAb) in women with unexplained recurrent miscarriage (RM).

Design: Observational, cohort study. The index cases included women with unexplained RM who tested positive for thyroid peroxidase antibody, and control cases included women with unexplained RM who tested negative for the antibodies; a second age-matched control group included women with RM who had a known cause for the repeated pregnancy loss.

Setting: Tertiary referral center for RM.

Patient(s): A total of 496 women with unexplained RM and 220 women with known diagnoses of RM who had a TPOAb test.

Intervention(s): Thyroxine replacement (50 μg daily during pregnancy) was begun in some patients who tested positive for thyroid peroxidase antibody, irrespective of TSH level.

Main Outcome Measure(s): Miscarriage and live birth rates of a subsequent pregnancy.

Result(s): A total of 496 women with unexplained RM who had a TPOAb test were included in the study. Of these, 10.7% of subjects tested positive for TPOAb. The prevalence of TPOAb in control subjects who had a known cause for RM was 11.8%. The live birth rate of the first pregnancies after referral was 64%, 53%, and 58% in TPOAb-negative, TPOAb-positive with thyroxine treatment, and TPOAb-positive without treatment subjects; there was no significant difference in the outcome between any two or three groups, or between those who tested positive or negative for TPOAb. Among women who tested positive for TPOAb, there was no difference in the antibody titer between women with unexplained RM and those with a known cause for the pregnancy loss. Women who tested positive for TPOAb were significantly more likely to have TSH levels above the normal range (≥4.2 mIU/L).

Conclusion(s): The prevalence of TPOAb-positive results in women with unexplained RM is not higher than in the general population, TPOAb-positive status does not have a prognostic value regarding the outcome of a subsequent pregnancy, and empirical thyroxine therapy in those who tested positive did not seem to improve outcome.