The analysis of primary and secondary outcomes will be controlled for study site, considering that the randomization is stratified by study site. The primary outcome (spontaneous vaginal delivery) and other categorical secondary outcomes will be compared between trial groups by using the Cochran-Mantel-Haenszel test. The estimates of the common relative risk and confidence intervals associated with the primary and secondary outcomes will be calculated. The Breslow-Day test for homogeneity of the odds ratios will be reported as well. Distributions of continuous secondary outcome measures such as duration of the second stage of labor within each site will be assessed by visual inspection of histograms and the Kolmogorov-Smirnov test. The mixed model in which study site is treated as a fixed effect will be used to compare normally distributed variables. If variables are not normally distributed, the van Elteren test will be used to make comparisons between the trial groups.