Predictors of Stillbirth Using a Large Database From the State of Wisconsin
Background: Stillbirth remains a significant problem in modern obstetrics. The exact causes for many stillbirths remain unexplained, although some risk factors have been identified.
Purpose: To identify the main risk factors for stillbirth using a large dataset, we examined incidence of stillbirth for the state of Wisconsin from 2012 through 2016.
Methods: We conducted a retrospective study using de-identified data for 323,034 pregnant women who gave birth to singleton babies in the years 2012 through 2016; 73% of the women were white, 11% African American and the remaining 16% were from other races. Birth weight percentage by gestational age was calculated using 10th and 90th percentile of the baby birth weight in grams and was divided into three groups (small, appropriate, large). Risk factors for stillbirth were explored using univariate and multivariable logistic regression analysis.
Results: Overall, the prevalence of stillbirth, defined in the United States as loss of a baby after 20 weeks of pregnancy, is about 1 in 160 pregnancies (6.3 per 1000). In the present study population from the state of Wisconsin, the rate of stillbirth was 4.1 per 1000. Mean age ± standard deviation for the women was 28.43 ± 5.5 years. The highest risk factor for stillbirth was small for gestational age (odds ratio [OR]: 15.6, 95% confidence interval [CI]: 13.7–17.8, P < 0.001), followed by diabetes (OR: 3.5, 95% CI: 2.5–5.1; P < 0.001), chronic hypertension (OR: 1.5, 95% CI: 1.1–1.9; P < 0.009), body mass index > 30 kg/m2 (OR: 1.5, 95% CI: 1.3–1.7; P < 0.001), and every 10-year increase in the age of the mother (OR: 1.2, 95% CI: 1.1–1.3; P < 0.003). In contrast, married women (OR: 0.8, 95% CI: 0.7–0.9; P = 0.009), women with higher education (OR: 0.7, 95% CI: 0.6–0.8, P < 0.001), and women receiving infant care (OR: 0.5, 95% CI: 0.4–0.6; P < 0.001) were less likely to have stillbirth.
Conclusion: Stillbirth prevalence in the state of Wisconsin is lower than the national average. Small for gestational age, which may be unrecognized intrauterine fetal growth restriction, was main predictor of stillbirth. Preventive strategies should focus on improving prenatal detection of fetal growth restriction, treatment of comorbid conditions such as diabetes and hypertension, and management for obesity among pregnant women.