The objective was to evaluate the pelvic floor muscles (PFM) in primigravidae and compare them with those in nonpregnant nulliparous women. The sample consisted of 141 women with a mean age of 22.8 years, divided into four groups: 36 nonpregnant nulliparous (C), 31 primigravidae in the first trimester (1T), 42 primigravida in the second trimester (2T), and 32 primigravidae in the third trimester (3T). The participants were examined by digital palpation for pelvic floor muscle contraction using the Modified Oxford Scale, by measuring maximal vaginal squeeze pressure with a vaginal perineometer, and by measuring PFM maximal strength using a vaginal dynamometer. The best value of three maximal strengths was considered for analysis, the Kruskal–Wallis and Mann–Whitney U tests were used and differences were considered significant at p ≤ 0.05. The mean values for group C were 3.2 (digital palpation), 45.6 cmH2O (perineometry), and 11.7 N (dynamometry); for group 1T the corresponding values were 2.5, 21.1 cmH2O, and 8.8 N; for group 2T: 2.8, 22.9 cmH2O, and 7.8 N; and for group 3T: 2.1, 17.3 cmH2O, and 6.8 N. Groups were compared in pairs for digital palpation, perineometry, and dynamometry. There were significant differences between group C and group 1T, and between group C and group 3T. There was a significant difference between group C and group 2T with regard to perineometry and dynamometry, but not digital palpation. Dynamometry demonstrated a difference between groups 1T and 3T, digital palpation between groups 2T and 3T. Pelvic floor muscles in primigravidae are not as strong as those in nonpregnant nulliparous women.