[Factors associated to the trial of labor in primipara women with one previous cesarean section].

OBJECTIVE The purpose of this study was to identify medical and non-medical factors associated to the performance of a trial of labor during the second delivery of women with one previous cesarean section. METHODS This was a nested case control study, with a secondary data analysis from a retrospective population based cohort study. It was primarily performed on a population of women who had had their first children in Campinas, SP, Brazil, during 1985. The study population was constituted of the 1,352 women of the cohort study who had had their first deliveries by cesarean section and also had their second deliveries no matter when. The group of cases (333 women, almost 25%) was constituted of those women who had a trial of labor during their second deliveries and the control group (1,019 women) of those who had not had it. For each possible associated factor evaluated, the Odds Ratio and its respective 95% Confidence Interval were calculated. For the ordered categorical variables, the chi2 for trend was also calculated. Finally, a non conditional multivariate regression analysis was performed, identifying the significant factors and then estimating their adjusted Odds Ratio. RESULTS The main factors associated with the trial of labor in this situation were a low monthly family income, having public medical insurance by the national health system, a low maternal age, the occurrence of rupture of membranes during the second delivery, and having been in childbirth during the first delivery. CONCLUSION It is concluded that the main determinants for a trial of labor among primipara women with one previous cesarean section were basically social and economic factors, rather than medical ones.