OBJECTIVE: To determine factors associated to vaginal delivery and increased neonatal mortality in cohort studies of newborns. METHODS: A retrospective cohort study was carried out using linkage data from the Information System on Live Births and Mortality Data System database, which included all newborns in Goiânia for the year 2000. A stratified analysis of delivery routes and maternity hospitals by risk factors of neonatal mortality was conducted through the calculation of relative risk at a 5% significance level. Statistical analyses were carried out using the Chi-square test at a 5% significance level. RESULTS: Vaginal deliveries were more commonly seen than cesarean sections in situations where there was an increased risk of neonatal mortality. Public hospitals, where vaginal deliveries predominated, were sought by the majority of those pregnant women with an increased risk of neonatal mortality. Private hospitals, not affiliated to the public-funded Brazilian Healthcare System (SUS) and where the incidence of cesarean section was as high as 84.9%, opted for vaginal delivery in situations of greater risk, such as extreme prematurity and very-low-birth-weight infants. CONCLUSIONS: The association between vaginal delivery and increase neonatal mortality resulted from a selection bias due to the distribution of pregnant women in the hospital network. In addition, this selection bias also resulted from an almost universal preference for cesarean sections in low-risk pregnancies as opposed to vaginal delivery for pregnancies with an increased risk of neonatal mortality.
Vaginal delivery; C-sections; Neonatal mortality; Risk factors; Low-birt-weight newborns; Private hospitals; Public hospitals; delivery, infant mortality, bias, epidemiological study; Brazilian Health Care System (SUS)
