1014 Introduction Pelvic organ prolapse (POP) is part of a range of conditions that are related to pelvic floor dysfunction such as urinary incontinence, bowel disorders and the report of vaginal bulging [1, 2]. The lifetime prevalence in women of over 50 years of age is 30–50% [3]. Women have an 11–11.8% chance of undergoing at least one surgical intervention for POP or incontinence by the age of 79 years, with a re- operation rate of 29.2% [4, 5]. Complication rates after surgery in different racial groups were reported to be 19.4% (white), 34.1% (black) and 27.4% (other) [6]. POP is therefore associated with a high financial burden on health care [4]. Although only a relatively small number of women with POP seek treatment, it is expected that this number will increase in the future [7]. At present, the direct cost of POP surgery already exceeds 1 $ billion per year in the United States alone [8]. To estimate the care requirements of women with POP in the future, it is important to have reliable prevalence data from a general female population. Data must be obtained using a questionnaire and vaginal examination because there is only a moderate correlation between the signs of POP (measured by vaginal examination) and the symptoms (measured by a questionnaire) [9, 10]. To obtain reference data on the prevalence and distribu- tion of POP signs and the POP symptom of feeling and/or seeing a vaginal bulge, we conducted a cross-sectional study on a general population of women aged 45–85 years. Our first aim was to develop and validate a prediction model that will be helpful to researchers and health care policy makers. We focussed on three different cut-off points because of a discrepancy between feeling and/or seeing a vaginal bulge (the cornerstone symptom of POP) and the presence of POP signs in literature. A high correlation between signs and symptoms can be present when a different cut-off point is taken regarding the presence of POP. Therefore, we looked at 1 cm above, at the hymen and 1 cm beyond the hymen. Secondly, we created a POP score chart and a prognostic index to estimate the presence of POP in a general population without vaginal examination and the amount of care needed by women. Materials and methods A cross-sectional study was performed on a general population of women aged 45 to 85 years. A flowchart of the study design is presented in Fig. 1. The study population comprised 2,979 women, regis- tered in the office records of eight out of nine general practitioners in Brielle. Brielle is a town near Rotterdam (the Netherlands) with 16,000 citizens. Because all inha- Int Urogynecol J (2009) 20:1013–1021 bitants have the obligation to be registered in a general practitioners clinic, the study population contained 95% of all women in Brielle. It has an almost exclusively white population (98.4%). Names and addresses of all 2,979 eligible women aged 45–85 years were obtained from the general practitioners. The women were sent information about the pelvic floor study and could be enrolled by filling out an informed consent form. They were offered three options: to sign a refusal form, or to fill out the questionnaire only or to fill out the questionnaire and undergo vaginal examination. All the women were asked to complete a self-report questionnaire. A reminder, containing the same question- naire, was sent 8 weeks after the first contact. The data were collected anonymously. To avoid selection bias, non- responders were invited to complete a short questionnaire that comprised five questions about age, parity, presence of stress urinary incontinence (yes/no), faecal incontinence (yes/no) and feeling of vaginal bulging (yes/no). To encourage a high response to the questionnaire, we used envelopes with the name and logo of the Erasmus University, coloured paper and stamped-addressed-return envelopes [11]. The questionnaire used in this study combined several Dutch validated pelvic floor questionnaires, such as the Urogenital Distress Inventory [12] and the Defaecation Distress Inventory [13]. In addition, subjects were asked about ethnicity, parity, vaginal bulging, incontinence, pelvic girdle pain and vaginal bulging during pregnancy, family history, menopausal status, hormone replacement therapy (HRT), previous pelvic floor surgery, educational level, smoking and heavy physical work at present or in the past. Vaginal examination From all the participants who gave informed consent in the beginning of the study to undergo vaginal examination (n= 1,140), 800 women were randomly selected by age for POPQ measurement. (All response forms of the women were registered with a number that identified the age, and they were at random taken by a research assistant). The POPQ was introduced by the International Continence Society (ICS). It has become widely accepted and proven to be valid [1] and reliable [14]. A gynaecologist (MV) and a physiotherapist (MS) performed the vaginal examinations. The two examiners practiced the POPQ measurement protocol until they reached agreement about the test and registration scores. This process was performed at the Pelvic Floor Centre at the Erasmus Medical Centre in Rotterdam. POPQ measure- ments were carried out in conformity with the ICS stand- ardisation report [1]. After each examination, all the details were entered into the three-by-three POPQ grid. The two