Impact of obstetric factors on outcome of extremely preterm births in Sweden: Prospective population-based observational study (EXPRESS)

Abstract

Introduction. A population-based observational study investigated the contribution of obstetric factors to the survival and postnatal development of extremely preterm infants. Material and methods. Mortality up to 1 year and neurodevelopment at 2.5 years (Bayley-III test, cerebral palsy, vision, hearing) were evaluated in infants born before 27 weeks of gestation in Sweden 2004-2007 (n = 1011), using logistic regression analyses of risk factors. Results. Of 844 fetuses alive at admission, 8.4% died in utero before labor, 7.8% died intrapartum. Of 707 live-born infants, 15% died within 24 h, 70% survived ≥365 days, 64% were assessed at 2.5 years. The risk of death within 24 h after birth decreased with gestational age [odds ratio (OR) 0.3; 95% CI 0.2-0.4], antenatal corticosteroids (OR 0.3; 95% CI 0.1-0.6), and cesarean section (OR 0.4; 95% CI 0.2-0.9); it increased with multiple birth (OR 3.0; 95% CI 1.5-6.0), vaginal breech delivery (OR 2.3; 95% CI 1.0-5.1), 5-min Apgar score <4 (OR 50.4; 95% CI 28.2-90.2), and birth at a level II hospital (OR 2.6; 95% CI 1.2-5.3). The risk of death between 1 and 365 days remained significantly decreased for gestational age and corticosteroids. The risk of mental developmental delay at 2.5 years decreased with gestational age, birthweight and fetal growth; it increased with vaginal breech delivery (OR 2.0; 95% CI 1.2-7.4), male gender, low Apgar score and high Clinical Risk Index for Babies score. Conclusion. Several obstetric factors, including abdominal delivery, influenced the risk of death within the first day of life, but not later. Antenatal corticosteroids and gestational age decreased the mortality up to 1 year. Mental developmental delay was related to vaginal breech delivery.