Associations between Hypothyroidism in Pregnancy and Adverse Maternal and Neonatal Outcomes: A cohort study

Abstract Objective This study aimed to determine associations between hypothyroidism during pregnancy and selected maternal and neonatal outcomes. Methods A retrospective, cohort study was conducted between January 2018 and December 2020 at the two main tertiary hospitals in Muscat, Oman. A total of 408 Omani pregnant women aged 18–45 years were included. Data from electronic medical records were compared between women with overt or subclinical hypothyroidism (n = 201; the exposed group) and those with normal thyroid function (n = 207; the matched unexposed group) to determine associations with selected outcomes. Results In terms of maternal outcomes, no significant differences were observed between exposed and unexposed groups with regards to the risk of gestational diabetes mellitus, pregnancy-induced hypertension, or pre-eclampsia ( P  > 0.05). However, pregnant women with hypothyroidism were twice as likely to exhibit iron deficiency anemia at delivery compared to women with normal thyroid function (relative risk [RR]: 2.22, 95% confidence interval [CI]: 1.68–2.94; P  < 0.001). Regarding neonatal outcomes, newborns born to mothers with hypothyroidism were less likely to be premature (RR: 0.83, 95% CI: 0.23–3.06), have low birth weight (RR: 0.86, 95% CI: 0.46–1.55), and exhibit macrosomia (RR: 0.52, 95% CI: 0.096–2.81) or abnormal cord TSH levels (RR: 0.21, 95% CI: 0.01–4.31); however, these associations were not statistically significant ( P  > 0.05). Conclusion Pregnant women with hypothyroidism were not found to be at increased risk of adverse maternal and neonatal outcomes compared to those without hypothyroidism. These findings could be attributed to the fact that most of the studied pregnant women with hypothyroidism were already receiving thyroxine replacement therapy, thereby achieving euthyroid status from a clinical and biochemical standpoint.