Examination of the pelvis, which is particularly important in nulliparous women, is intended to detect any anatomical anomalies that could have an influence on the mechanics of labor. The objective of the present study was to evaluate the relationship between Trillat's prepubic and bi-ischiatic diameters and obstetrical outcome in nulliparous women. It was a descriptive cross-sectional study with an analytical component in 400 nulliparous pregnant women received from February 2016 to August 2017 in ANC and labor rooms of different selected hospitals in the city of Lubumbashi. The base of Trillat's triangle and the bi-ischiatic diameter were respectively measured (in cm) using a metric tape and Breisky's pelvimeter in order to evaluate their relationship on obstetrical outcome (vaginal route or cesarean section) in vertex presentation. The following statistical tests were used: Kolmogorov-Smirnov test, Pearson chi-square, Fisher exact test, Wilcoxon, Kruskal Wallis, Mantel Haenszel. The significance level was set at p<0.05.