The Effect of Subclinical Maternal Thyroid Dysfunction and Autoimmunity on Intrauterine Growth Restriction: A Systematic Review and Meta-Analysis.

The objective of this study was to evaluate the association between maternal subclinical thyroid dysfunction and autoimmunity with the risk for intrauterine growth restriction (IUGR).Design is a systematic review and meta-analysis.A literature search was conducted using PubMed, Embase, and Cochrane database. A combination of 2 key words was used to search for the eligible studies: one indexed thyroid dysfunction or antithyroid antibodies; and the other one indexed the adverse neonatal outcomes of pregnancy, such as IUGR, small for gestational age, fetal growth restriction, or low birth weight.Two reviewers selected the studies, and eligible studies met the following criteria: prospective cohort studies or case control studies, studies of maternal thyroid dysfunction and positive antithyroid antibodies as the exposure of interest, and studies of IUGR or small for gestational age as the outcome of interest.Data were recorded, including data from maternal thyroid disorders and IUGR, and compared with a reference group.There were 22 individual data from the 13 cohort articles. Among these, 7 were focused on subclinical hypothyroidism (SCH), 4 on subclinical hyperthyroidism, 7 on positivity for thyroid peroxidase antibody (TPOAb), and 4 on isolated hypothyroxinemia. Meta-analysis showed that there was no effect of subclinical hyperthyroidism (odds ratio (OR) = 0.98; 95% confidence interval (CI), 0.40-2.41), TPOAb positivity (OR = 1.57; 95% CI, 0.77-3.18), or isolated hypothyroxinemia (OR = 1.05, 95% CI: 0.37-2.92) on IUGR. However, SCH is associated with IUGR (OR = 1.54; 95% CI, 1.06-2.25).SCH is associated with IUGR; however, subclinical hyperthyroidism, TPOAb positivity, or isolated hypothyroxinemia do not affect the risk of IUGR.