Associations of maternal iodine status and thyroid function with adverse pregnancy outcomes in Henan Province of China

Objective: The study aimed to explore the effects of maternal iodine status and thyroid diseases on adverse pregnancy outcomes. Methods: A prospective study was conducted on 2347 pregnant women, who provided 2347 urinary samples tested for iodine, 1082 serum samples tested for thyroid function, and 2347 questionnaires about demographic information. Their pregnancy outcomes were recorded and compared between different urinary iodine concentration (UIC) and thyroid function groups. Results: Pregnant women with UIC between 150 and 249 mu g/L had lower incidences of preeclampsia (adjusted odds ratio (OR) 0.12, 95% CI: 0.01-0.87), placenta previa (adjusted OR 0.06, 95% CI: 0.01-0.69) and fetal distress (adjusted OR 0.10, 95% CI: 0.02-0.64) than the reference group (UIC < 50 mu g/L). Women with UIC between 100 and 149 mu g/L had lower risks of abnormal amniotic fluid (adjusted OR 0.32, 95% CI: 0.12-0.87) and fetal distress (adjusted OR 0.08, 95% CI: 0.01-0.82). Women with UIC above 249 mu g/L. had a significant higher rate of abnormal amniotic fluid (adjusted OR 0.38, 95% CI: 0.16-0.89). Clinical and subclinical hypothyroidism during pregnancy increased the risk of preterm delivery by 4.4 times (P = 0.009) and 3.0 times (P = 0.014), respectively. Isolated hypothyroxinemia had increased odds of having macrosomia (adjusted OR 2.22, 95% CI: 1.13-4.85). Clinical hyperthyroidism was significantly associated with miscarriage (adjusted OR 2.12, 95% CI: 1.92-96.67) and fetal distress (adjusted OR 9.53, 95% CI: 1.05-81.81). Subclinical hyperthyroidism had a significant association with umbilical cord entanglement (adjusted OR 3.82, 95% CI: 1.38-10.58). Isolated hyperthyroxinemia was associated with preterm delivery (adjusted OR 4.73, 95% CI: 1.49-15.05). Conclusions: Maternal iodine status and thyroid diseases during pregnancy were associated with adverse pregnancy outcomes.