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

IntroductionA population-based observational study investigated the contribution of obstetric factors to the survival and postnatal development of extremely preterm infants. Material and methodsMortality up to 1year and neurodevelopment at 2.5years (Bayley-III test, cerebral palsy, vision, hearing) were evaluated in infants born before 27weeks of gestation in Sweden 2004-2007 (n=1011), using logistic regression analyses of risk factors. ResultsOf 844 fetuses alive at admission, 8.4% died in utero before labor, 7.8% died intrapartum. Of 707 live-born infants, 15% died within 24h, 70% survived 365days, 64% were assessed at 2.5years. The risk of death within 24h 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 365days 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. ConclusionSeveral 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 1year. Mental developmental delay was related to vaginal breech delivery.