Figure 2:

Percentile plots illustrating the distributions of four outcomes (A-D), each comparing women classified according to the presence or absence of levator ani avulsion and history of forceps-assisted birth: (A) levator hiatus area with Valsalva; (B) genital hiatus with Valsalva; (C) change in levator hiatus area with voluntary contraction (rest minus contraction); (D) pelvic muscle strength (peak pressure) with voluntary contraction. P values derived from linear regression.