Pregnancy outcomes among women with thyrotoxicosis a retrospective cohort study

Abstract Objective: To compare adverse outcomes between: 1) pregnant women with thyrotoxicosis and low risk pregnancies, 2) pregnant women with thyrotoxicosis requiring no anti-thyroid drug (ATD) and low risk pregnancies, and 3) those treated with methimazole (MMI) and propylthiouracil (PTU)Methods: The medical records of singleton pregnancies with thyrotoxicosis were comprehensively reviewed. Low-risk pregnancies matched for age and parity were randomly recruited as controls. The obstetric outcomes were compared between both groups, and the outcomes of various subgroups of the study group were also compared.Results: A total of 408 pregnant women with thyrotoxicosis were recruited. Compared with the controls, the women of the study group had significantly higher rates of low birth weight (LBW) (23.7% vs 17.7%; p:0.036), preterm birth (19.3% vs 12.3%; p:0.007), preeclampsia (8.5% vs 4.4%; p: 0.019) and cesarean section (21.5% vs 16.0%; p:0.046). In the study group (thyrotoxicosis), 67, 127, and 158 patients were treated with MMI, PTU and no anti-thyroid drug (ATD), respectively. All obstetric outcomes were comparable between the women treated with PTU and those with MMI, and between the controlled and uncontrolled groups. However, women who needed ATD had significantly higher rates of LBW and preterm birth than those without medications.Conclusions: Thyrotoxicosis, whether treated or not needing ATDs, was significantly associated with an increased risk of adverse pregnancy outcomes. Also, active disease, indicated by the need for ATD significantly increased the risk of such adverse outcomes, whereas the patients treated with MMI or PTU had comparable adverse outcomes.