Risk factors for not delivering in a level III unit before 32 weeks of gestation: results from a population-based study in Paris and surrounding districts in 2003.

Delivery of very preterm babies in maternity units with on-site neonatal intensive care (level III units) is associated with lower mortality and morbidity. This analysis explores risk factors for not delivering in a level III unit, using data from a population-based study of very preterm births in Paris and surrounding districts in 2003. The sample for analysis included resident women with a fetus alive at the onset of labour between 24 and 31 weeks of gestation (n = 641). Characteristics of women delivering in and those not in level III units were compared using logistic regression. Further analysis was carried out for the subgroup of women not already scheduled to deliver in a level III unit. Twenty-nine per cent of women did not deliver in level III units; in the subgroup scheduled to deliver in level I or II units, 43% were not transferred. Women were less likely to deliver in a level III unit if they had a singleton pregnancy, a gestation of <26 weeks or at 31 weeks, experienced antenatal haemorrhaging, lived in socially deprived neighbourhoods or at a greater distance from the nearest level III. Women scheduled to deliver in a maternity unit with a special care nursery were also less likely to deliver in a level III unit. In contrast, preterm rupture of membranes and fetal growth restriction increased the likelihood of a level III delivery. These results underline the importance of controlling for clinical characteristics when analysing perinatal outcome by place of delivery and show how socioeconomic factors, known to impact on the risk of having a preterm birth, can also affect access to appropriate care.