Low birth weight and preeclampsia in pregnancies complicated by hyperthyroidism.

OBJECTIVE

To determine whether control of hyperthyroidism during pregnancy reduces the risk of low birth weight infants and severe preeclampsia.

METHODS

Labor, delivery, and postpartum records of 181 hyperthyroid women were reviewed for maternal and fetal outcomes. Subjects were separated into three groups based on their thyroid status: controlled (n = 34), including women who were euthyroid at presentation and delivery; controlled during pregnancy (n = 90), including women who were hyperthyroid at presentation and euthyroid at delivery; and uncontrolled (n = 57), including women who were hyperthyroid at presentation and delivery.

RESULTS

The risk of low birth weight infants was 0.74 (95% confidence interval [CI] 0.18-3.08) among controlled women, 2.36 (95% CI 1.36-4.12) among women who were controlled during pregnancy, and 9.24 (95% CI 5.47-15.6) among women who were uncontrolled during pregnancy compared to the incidence among nonhyperthyroid mothers. The risk of severe preeclampsia was significantly higher (odds ratio 4.74, 95% CI 1.14-19.7) among uncontrolled women compared with those who were controlled during their pregnancies. Elevated TSH-receptor antibody levels were not related to preeclampsia. Maternal thioamide therapy did not adversely affect neonatal outcomes.

CONCLUSION

Lack of control of hyperthyroidism significantly increases the risk of low birth weight infants and severe preeclampsia.