Objective To determine if differences exist in the collagen status of premenopausal nulliparous women with genuine stress incontinence compared with continent controls.

Design Thirty-six premenopausal nulliparous women with urodynamically-proven genuine stress incontinence were compared with 25 controls. All the women studied had a periurethral vaginal biopsy taken of approximately 30–50 mg in wet weight. This biopsy was then analysed to determine the collagen content, the type I:III collagen ratio and the collagen cross-link content.

Setting A tertiary referral urodynamic unit.

Results The nulliparous women with genuine stress incontinence had significantly less collagen in their tissues (P < 0.0001) compared with the continent controls. In addition, there was a decreased ratio of type I to type III collagen (P= 0.0008), and the cross-link content was also significantly reduced in the women with genuine stress incontinence (P < 0.0001).

Conclusion Genuine stress incontinence is present in a significant number of women before childbirth. The aetiology of their incontinence appears to be due to a defect in their connective tissue, with both a quantitative and qualitative reduction in their collagen.