INTRODUCTION: Early-onset neonatal sepsis (EONS) is an important cause of neonatal morbidity and mortality and is strongly associated with intra-amniotic infection. The risk of intra-amniotic infection increases after preterm prelabor rupture of membranes (PPROM). Better tools are needed for monitoring women with PPROM for intra-amniotic infection and identifying those at high risk of EONS so that intervention can be made timely. This study aimed to identify antepartum risk factors for EONS in a PPROM population and develop a risk-indicating model.

MATERIAL AND METHODS: We performed a historical cohort study on PPROM pregnancies delivering between gestational weeks 24 + 0 and 33 + 6 in Stockholm, Sweden. Using logistic regression, we evaluated the risk of the outcome EONS associated with maternal background characteristics, symptoms and signs, and cardiotocography. We combined variables associated with high risk into a risk-indicating model and estimated its performance by calculating its sensitivity, specificity, accuracy, positive and negative predictive values, positive likelihood ratio, and area under the ROC curve.

RESULTS: We included 709 women and their neonates, out of which 29 developed EONS. Variables most strongly associated with EONS were maternal diabetes (OR 4.37, 95% CI 1.41-13.56), maternal temperature ≥ 38°C (OR 6.42, 95% CI 2.94-14.02), positive urinary or vaginal/cervical culture (OR 2.62, 95% CI 1.14-6.03), and cardiotocography parameters. Fetal baseline frequency above 160 bpm was associated with a 3.75 times increased risk of EONS (95% CI 1.51-9.33). Meanwhile, short-term variation was negatively associated with EONS risk, and a value below 4 ms had a 4.17 times increased risk of EONS (95% CI 1.77-9.83). A risk-indicating model for EONS combining the mentioned variables had an area under the ROC curve of 0.7348. This model performed better at indicating risk for EONS than the clinicians' suspicion of intra-amniotic infection.

CONCLUSIONS: Maternal diabetes, maternal fever, positive urinary or vaginal/cervical culture, fetal tachycardia, and decreasing short-term variation were associated with an increased risk for EONS in a PPROM population. A risk-indicating model combining these risk factors performed better than the clinicians' suspicion of intra-amniotic infection in identifying high-risk pregnancies for EONS.