Identifying predictors and developing a risk score for preterm birth among Kenyan pregnant women

Abstract

Background: Preterm birth (PTB) is a leading cause of neonatal mortality, particularly in sub-Saharan Africa where 40% of global neonatal deaths occur. We identified and combined correlates of PTB among Kenyan women to develop a risk score. Methods: We used data from a prospective study enrolling HIV-negative women from 20 antenatal clinics in Western Kenya (NCT03070600). Depressive symptoms were assessed by study nurses using the Center for Epidemiologic Studies Depression Scale (CESD-10), intimate partner violence (IPV) with the Hurt, Insult, Threaten, Scream scale (HITS), and social support using the Medical Outcomes Survey scale (MOS-SSS). Predictors of PTB (birth <37 weeks gestation) were identified using multivariable Cox proportional hazards models, clustered by facility. We used stratified k-fold cross-validation methods for risk score derivation and validation. Area under the receiver operating characteristic curve (AUROC) was used to evaluate discrimination of the risk score and Brier score for calibration. Results: Among 4084 women, 19% had PTB (incidence rate: 70.9 PTB per 100 fetus-years (f-yrs)). Predictors of PTB included being unmarried (HR:1.29, 95% CI:1.08-1.54), lower education (years) (HR:0.97, 95% CI:0.94-0.99), IPV (HITS score ≥5, HR:1.28, 95% CI:0.98-1.68), higher CESD-10 score (HR:1.02, 95% CI:0.99-1.04), lower social support score (HR:0.99, 95% CI:0.97-1.01), and mild-to-severe depressive symptoms (CESD-10 score ≥5, HR:1.46, 95% CI:1.07-1.99). The final risk score included being unmarried, social support score, IPV, and MSD. The risk score had modest discrimination between PTB and term deliveries (AUROC:0.56, 95% CI:0.54-0.58), and Brier Score was 0.4672. Women considered “high risk” for PTB (optimal risk score cut-point) had 40% higher risk of PTB (83.6 cases per 100 f-yrs) than “low risk” women (59.6 cases per 100 f-ys; HR:1.6, 95% CI:1.2-1.7, p<0.001). Conclusion: A fifth of pregnancies were PTB in this large multisite cohort; PTB was associated with several social factors amenable to intervention. Combining these factors in a risk score did not predict PTB, reflecting the multifactorial nature of PTB and need to include other unmeasured factors. However, our findings suggest PTB risk could be alleviated by integrating mental health and support services into routine antenatal care.