Impact of obstetric factors on outcome of extremely preterm births in Sweden: prospective population‐based observational study (<scp>EXPRESS</scp>)

<jats:title>Abstract</jats:title><jats:sec><jats:title>Introduction</jats:title><jats:p>A population‐based observational study investigated the contribution of obstetric factors to the survival and postnatal development of extremely preterm infants.</jats:p></jats:sec><jats:sec><jats:title>Material and methods</jats:title><jats:p>Mortality up to 1 year and neurodevelopment at 2.5 years (Bayley‐<jats:styled-content style="fixed-case">III</jats:styled-content> test, cerebral palsy, vision, hearing) were evaluated in infants born before 27 weeks of gestation in Sweden 2004–2007 (<jats:italic>n</jats:italic> = 1011), using logistic regression analyses of risk factors.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>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 (<jats:styled-content style="fixed-case">OR</jats:styled-content>) 0.3; 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 0.2–0.4], antenatal corticosteroids (<jats:styled-content style="fixed-case">OR</jats:styled-content> 0.3; 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 0.1–0.6), and cesarean section (<jats:styled-content style="fixed-case">OR</jats:styled-content> 0.4; 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 0.2–0.9); it increased with multiple birth (<jats:styled-content style="fixed-case">OR</jats:styled-content> 3.0; 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 1.5–6.0), vaginal breech delivery (<jats:styled-content style="fixed-case">OR</jats:styled-content> 2.3; 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 1.0–5.1), 5‐min Apgar score <4 (<jats:styled-content style="fixed-case">OR</jats:styled-content> 50.4; 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 28.2–90.2), and birth at a level <jats:styled-content style="fixed-case">II</jats:styled-content> hospital (<jats:styled-content style="fixed-case">OR</jats:styled-content> 2.6; 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 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 (<jats:styled-content style="fixed-case">OR</jats:styled-content> 2.0; 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> 1.2–7.4), male gender, low Apgar score and high Clinical Risk Index for Babies score.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>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.</jats:p></jats:sec>