To provide evidence that primary vestibulodynia (PV) is a congenital defect in tissue derived from the primitive urogenital sinus.Twenty-two women with PV, 16 with secondary vestibulodynia (SV) and 8 controls were included in this study. Subjects underwent a complete history and physical examination, including assessment with a vulvalgesiometer to measure the sensory and pain detection thresholds in the vulvar vestibule, deltoid and umbilicus.The median vestibular sensitivity was 5 g in the PV group and 10 g in the SV group (p= 0.77). The median umbilical pain thresholds for the PV, SV and control groups were 115, 675 and 500 g, respectively. Women with PV displayed a significantly higher level of umbilical sensitivity (a substantially lower pain threshold) compared with women with SV and the control group (p = 0.0001 and 0.002, respectively). There was no difference in umbilical sensitivity between the SV and control groups.Because both the umbilicus and vulvar vestibule are derived from primitive urogenital sinus, this suggests that women with PV may have a congenital abnormality in urogenital - sinus-derived epithelium.