Prolonged passive second stage of labor in nulliparous women—Prevalence and risk factors: A historical cohort study

Introduction: This study examined the prevalence of and risk factors for a prolonged passive second stage of labor in nulliparous women. Material and Methods: This was a historical cohort study of all nulliparous women (n = 1131) at two delivery units in Sweden. Maternal and obstetric data were obtained from electronic medical records during 2019. Duration of the passive second stage was measured as time from retracted cervix to start of pushing. Prolonged passive second stage was defined as ≥2 h. Prevalence was calculated and associations between prolonged passive second stage and maternal, obstetric and neonatal characteristics and potential risk factors were assessed using logistic regression models. Results: The prevalence of prolonged passive second stage was 37.6%. Factors associated with an increased risk of prolonged passive second stage were epidural analgesia (adjusted odds ratio [aOR] 3.93; 95% confidence interval [CI] 2.90–5.34), malpresentation (aOR 2.26; 95% CI 1.27–4.05), maternal age ≥ 30 years (aOR 2.00; 95% CI 1.50–2.65) and birth weight ≥ 4 kg (aOR 1.50; 95% CI 1.05–2.15). Maternal body mass index ≥30 (aOR 0.52; 95% CI 0.34–0.79) and noncohabiting (aOR 0.51; 95% CI 0.30–0.89) reduced the odds of prolonged passive second stage. Conclusions: A prolonged passive second stage of labor in nulliparous women is common (n = 425 [38%]). We found epidural analgesia, malpresentation, maternal age ≥ 30 years and birthweight ≥4 kg to be major risk factors associated with an increased risk of a prolonged passive second stage. Birth outcomes for prolonged passive second stage need to be investigated to strengthen evidence for the management of the second stage of labor.