Between 2004 and 2014, there were 9,096,788 deliveries; 16,984 of them had the diagnosis of hyperthyroidism, by far the largest studied population in the literature. The rest were categorized as a nonhyperthyroidism group. The main portion of the deliveries in both the hyperthyroidism group and the nonhyperthyroidism group had occurred between age 25 and 34 years old, and to Caucasians. Pregestational medical conditions such as obesity, hypertension, and diabetes mellitus were more prevalent in women who suffered from hyperthyroidism compared with the nonhyperthyroidism group (4.5% vs. 3.6% for obesity, 5.7% vs. 1.8% for hypertension, and 2.1% vs. 0.9% for diabetes, respectively). All baseline demographic characteristics are summarized in Table 1.
All pregnancy outcomes were adjusted for age, race, plan type, obesity, chronic hypertension, recreational drugs use, previous cesarean section, smoking during pregnancy, multiple gestation, pregestational diabetes, in vitro fertilization, hospital type, and income. After adjusting for those confounders in a multivariable analysis, our study shows that women with hyperthyroidism were more likely to suffer from hypertensive disorders during pregnancy: they had more gestational hypertension (p = .013), preeclampsia (p = .042), and eclampsia (p = .035). Although the number of cases of eclampsia were small and should be verified in a subsequent study. Maternal hyperthyroidism was also found to be associated with preterm premature rupture of membranes (p = .044), preterm delivery (p < .001), and placenta previa (p = .016). Cesarean section rates did not differ statistically between the two groups (37.7% in the hyperthyroidism group, 32.3% in the nonhyperthyroidism group, p = .251). Although pregestational diabetes was higher in hyperthyroid mothers, gestational diabetes was not statistically different between the two groups (p = .124). We noted an increased risk for deep vein thrombosis (p = .036) and venous thromboembolism (p = .010) in the hyperthyroid group. The crude and adjusted ORs for the association between pregnancy and delivery outcomes and their respective prevalence in each cohort are outlined in Table 2.
All infant outcomes (Table 3) were adjusted for age, race, plan type, obesity, chronic hypertension, recreational drugs use, previous cesarean section, smoking during pregnancy, multiple gestation, pregestational diabetes, in vitro fertilization, hospital type, income, gestational hypertension, preeclampsia, eclampsia, and placenta previa. Children born to mothers who suffered from hyperthyroidism were more likely to be small for gestational age (p < .001) and had a higher risk of stillbirth (p = .013). Congenital anomalies were similar in the hyperthyroid and control groups (0.6% compared with 0.4% in the nonhyperthyroid group, p = .131).
Clin Endocrinol. 2022;97(3):347-354. © 2022 Blackwell Publishing