Risk factors for seizures in the vigorous term neonate: A population-based register study of singleton births in Sweden.

Background: Neonatal seizures have been associated with increased mortality and impaired neurodevelopment and, knowledge about risk factors may be useful for prevention. Clear associations have been established between labor-related risk factors and seizures in asphyxiated neonates. However, there is limited information about why some vigorous term-born infants experience seizures.

Objectives: Our aim was to assess antepartum and intrapartum risk factors for seizures in vigorous term-born neonates.

Methods: This was a national cohort study of singleton infants born at term in Sweden from 2009-2015. Vigorous was defined as an Apgar score of at least 7 at 5 and 10 minutes. Data on the mothers and infants were obtained from the Swedish Medical Birth Register and the Swedish Neonatal Quality Register. A diagnosis of neonatal seizures was the main outcome measure and the exposures were pregnancy and labor variables. Logistic regression analysis was used and the results are expressed as adjusted odds ratios (aOR) with 95% confidence intervals (CI).

Results: The incidence of neonatal seizures was 0.81/1,000 for 656 088 births. Seizures were strongly associated with obstetric emergencies (aOR 4.0, 95% CI 2.2-7.4), intrapartum fever and/or chorioamnionitis (aOR 3.4, 95% CI 2.1-5.3), and intrapartum fetal distress (aOR 3.0, 95% CI 2.4-3.7). Other associated intrapartum factors were: labor dystocia, occiput posterior position, operative vaginal delivery, and Cesarean delivery. Some maternal factors more than doubled the risk: a body mass of more than 40 (aOR 2.6, 95% CI 1.4-4.8), hypertensive disorders (aOR 2.3, 95% CI 1.7-3.1) and diabetes mellitus (aOR 2.6, 95% CI 1.7-4.1).

Conclusion: A number of intrapartum factors were associated with an increased risk of seizures in vigorous term-born neonates. Obstetric emergencies, intrapartum fever and/or chorioamnionitis and fetal distress were the strongest associated risks. The presence of such factors, despite a reassuring Apgar score could prompt close surveillance.