Is parity in the eye of the beholder?

To investigate whether parity status can be predicted by physical examination and which findings are most predictive. A retrospective chart review of 75 postmenopausal nulliparous/parous sister pairs who underwent gynecological examination as part of a study. An examiner, blinded to parity status, predicted parity status based on physical findings recorded on 146 women. Parity status was correctly predicted for 84.9% of the women. Of the 22 women for whom parity prediction was incorrect, 11 were nulliparous and 11 parous. The physical findings most commonly used for prediction were presence or absence of abdominal striae, appearance of the cervical os, and condition of hymen. Absence of the hymen at 6 o'clock alone correctly predicted parity in 11 of 12 parous and 11 of 11 nulliparous women. Parity status can be predicted based on physical exam in the majority of women. Blinding of investigators to parity status may not be feasible.