Hyperthyroidism as a Potential Risk Factor for Placental Abruption: A Case Control Study

BackgroundOvert hyperthyroidism and hypothyroidism are associated with pregnancy complications; however, most women with these conditions are diagnosed before conception and are under treatment during pregnancy, especially in the developed countries. The purpose of this study was to investigate pregnancy complications among these women.MethodsA retrospective case-control study was conducted, and data on 3824 pregnant women who gave birth at Nagoya University Hospital located in Japan from 2005 to 2014 was collected. The pregnancy outcomes were divided and compared among three groups: the control group (n = 3709), the hyperthyroidism group (n = 52) and the hypothyroidism group (n = 63). Risk factors for placental abruption were also evaluated in singleton pregnancies (n = 3588) by multivariable logistic regression analysis. Moreover, in hyperthyroidism, thyroid function was also compared between successful and failed placentation group, and the latter group included placental abruption and preeclampsia. ResultsThe incidence of placental abruption was significantly higher in hyperthyroidism than in control and hypothyroidism groups (p < 0.01). Hyperthyroidism was independently associated with an increased risk of placental abruption (adjusted odds ratio = 12.52, 95% confidence interval = 2.91–53.88). Thyroid stimulating hormone (TSH) was significantly lower in failed placentation group than in successful placentation group (p < 0.05). ConclusionAccording to the results of our study, pregnancy outcomes in women with treated hypothyroidism were comparable with those in women without thyroid disease. Conversely, women with treated hyperthyroidism showed an independent risk of placental abruption, which might be related with lower TSH level at early gestation. However, further research is required to validate our findings.