Medically indicated late preterm delivery and its impact on perinatal morbidity and mortality: a retrospective population-based cohort study

<b>Objective:</b> In the last few decades, attention has been focused on morbidity and mortality associated with late preterm delivery (34–36 + 6/7 weeks), accounting for 60–70% of all preterm births. This study is aimed to determine (1) the prevalence of late preterm deliveries (spontaneous and medically indicated) in our population; and (2) the rate of neonatal morbidity and mortality as well as maternal complications associated with the different phenotypes of late preterm deliveries. <b>Study design:</b> This retrospective population-based cohort study, included 96,176 women who had 257,182 deliveries, occurred between 1988 and 2011, allocated into three groups: term (<i>n</i> = 242,286), spontaneous (<i>n</i> = 10,063), and medically indicated (<i>n</i> = 4833) late preterm deliveries. <b>Results:</b> (1) Medically indicated late preterm deliveries were associated with increased maternal morbidity, as well as neonatal morbidity and mortality, in comparison with other study groups (<i>p</i> <b>Conclusions:</b> (1) Medically indicated late preterm deliveries were independently associated with adverse composite neonatal outcome; and (2) to benefit in term of neonatal outcome from the tool of medically indicated late preterm birth, their proportion should be kept below 35% of all late preterm deliveries, while exceeding this threshold increases the risk of neonatal mortality.