Maternal Thyroid Disease and Neonatal Low Birth Weight: A Systematic Review and Meta-Analysis

Objective: Thyroid disorder is a common endocrine complication in pregnant women: the association between neonatal low birth weight (LBW) and thyroid dysfunction during pregnancy has not been definitely confirmed. We conduct a systematic literature review and meta-analysis of the adverse fetal complication of LBW in maternal thyroid disease, including overt and subclinical hyperthyroidism and hypothyroidism. Methods: Relevant studies in English published between 1990 and 2016 were identified by searching PubMed, Medicine, and Embase databases. Cohort studies that evaluated the association between LBW infants and overt and subclinical hyperthyroidism or hypothyroidism during pregnancy and included a healthy pregnancy reference group were selected. The combined odds ratio (OR) with 95% confidence intervals (CI) were calculated to evaluate this relationship. Results: A total of 11 cohort studies (1,171,052 participants) assessed the association between maternal thyroid disease and LBW infants. An increased risk for LBW in hyperthyroidism pregnancies was demonstrated (OR: 1.30, 95% CI 1.11 1.54; p = 0.02). No significant increased risk for LBW was detected in subclinical hyperthyroidism (OR 1.03; 95% CI 0.72 1.48; p = 0.87), or hypothyroidism pregnancies (overt: OR 0.98; 95% CI 0.88 1.10; p = 0.75; subclinical: OR 1.29; 95% CI 0.81 2.04; p = 0.28). Conclusion: Data show a higher trend towards an increased risk of LBW among infants from maternal hyperthyroidism pregnancies. No association was seen in subclinical cases of hyperthyroidism or hypothyroidism during pregnancy.