Thyroid autoimmunity and miscarriage: a meta-analysis

To investigate whether thyroid autoimmunity (TAI) is associated with increased risk of miscarriage in euthyroid women.

An electronic search was conducted using the databases Medline, PubMed, EMBASE and the Cochrane library, from inception to October 2010. A systematic review of the studies on the association between TAI and miscarriage was performed. The odd ratios of case-control studies and relative risks of cohort studies were pooled respectively. The software Review Manager (version 4.3.1) was applied for meta-analysis.

The search strategy identified 53 potentially relevant publications, 22 of which were included in the meta-analysis. A clear association between thyroid autoimmunity and miscarriage was observed with a pooled odds ratio of 2·55 (95% CI 1·42-4·57, P=0·002) in eight case-control studies and a pooled relative risk of 2·31 (95% CI 1·90-2·82, P<0·000 01) in 14 cohort studies. Women with TAI were found to have slightly higher age [age difference, 1·29 years] (95% CI 0·43-2·16, P=0·003) and thyroid-stimulating hormone (TSH) levels [TSH difference, 0·61 mIU/l] (95% CI 0·51-0·71, P<0·000 01) compared with those without TAI.

Based on the currently available evidence, it appears that the presence of thyroid autoimmunity is associated with an increased risk of spontaneous miscarriage in euthyroid women.