Impact of risk factors for perinatal events in Japan: Introduction of a newly created perinatal event score.

Aim: A cohort study was performed to clarify the influence of risk factors on perinatal events (obstetric complications and/or perinatal deaths).

Methods: This cohort study reviewed 395 785 births from 2011 to 2013. Women with singleton pregnancies delivered after 22 weeks of gestation were included. The OR were determined on multivariate analysis. The perinatal event score (PES) for risk factors, which is the product of the OR of risk factors for obstetric complications, OR of risk factors for perinatal death, and OR of obstetric complications for perinatal death, was introduced to clarify the impact of each risk combination.

Results: There were 20 risk factors such as maternal age and medical complications relating to the 11 obstetric complications, including pregnancy-induced hypertension and preterm labor. As a result, 77 combinations of risk factors and obstetric complications were found to be significant. Six obstetric complications such as preterm labor and cervical insufficiency were found to be related to perinatal death. Two factors were found to be directly related to perinatal death: age >40 years old (OR, 1.24; 95%CI: 1.11-1.39) and essential hypertension (OR, 1.56; 95%CI: 1.19-2.05). As a result, PES ranged from 1.07 (primipara for premature rupture of membrane) to 40.1 (essential hypertension for placental abruption), and high PES (≥8) was identified in 21 combinations of risk factors and obstetric complications.

Conclusion: This newly created score for perinatal events, PES, can be used as an indicator of the impact of risk factors on perinatal events.