Assisted reproduction and thyroid autoimmunity: An unfortunate combination?

The association between positive thyroid antibodies and an increased miscarriage rate in pregnancies after assisted reproduction technology ( ART) remains controversial. We wanted to clarify this issue by performing a prospective cohort study in 234 women by systematically screening for thyroid peroxidase antibodies (TPO-Ab), serum TSH, and free T-4 (FT4) before the first ART cycle. Women with overt thyroid dysfunction were excluded. Fourteen percent of the cohort had positive TPO-Ab. Baseline characteristics [ age, 33 +/- 5 yr; TSH, 1.6 (0.02-4.1) mU/liter; and FT4, 12.2 (9.1 - 18) ng/ liter] were comparable to those of the 86% of women without antibodies [age, 32 +/- 5 yr; TSH, 1.3 0.05 - 3.6) mU/liter; and FT4, 11.7 (9.5 - 16.5) ng/liter]. In the antibody-positive group, the pregnancy rate was 53% vs. 43% in the antibody-negative group, with an odds ratio of 0.67 [95% confidence interval (CI) (0.32 - 1.41); P = not significant]; however within the group that was pregnant, the miscarriage rate was 53% and 23%, respectively, with an odds ratio of 3.77 [ 95% CI (1.29- 11.05); P = 0.016]. The age of the women was an independent risk factor for miscarriage, odds ratio 1.08 [ 95% CI (1.03 - 1.15); P = 0.005]. We conclude that women with positive TPO-Ab before the first ART cycle have a significantly increased risk for miscarriage.