The pelvic floor, honestly
Long-term data, and the one thing that reliably helps.
In a cohort of 3,763 women followed for 12 years after birth, 37.9% had persistent urinary incontinence. Of the women who had incontinence at 3 months, 76.4% still had it at 12 years. Delivering exclusively by cesarean was protective (odds ratio 0.42) but a mixed history of cesarean and vaginal birth was not.
At 15 to 23 years after a first birth, compared with a normal vaginal birth, cesarean was associated with less symptomatic prolapse (adjusted odds ratio 0.42) and less incontinence (0.65), while forceps or vacuum delivery was associated with more prolapse (1.73) and more faecal incontinence (1.96).
Pelvic floor muscle training works best as prevention. Across the trials, training during pregnancy in women who were still continent reduced incontinence in late pregnancy by 62% (relative risk 0.38) and at 3 to 6 months after birth by 29% (relative risk 0.71). Started after incontinence is established, the evidence of benefit was not clear.