Childbirth versus pelvic floor stability: An evolutionary history of compromises

A human pelvis and muscles of the pelvic floor, which span the bony pelvic canal. The model (1, transparent cyan) used in the analysis is shown superimposed on the pelvic floor muscles (2, red ). Katya Stansfield) - Human childbirth is comparatively difficult because our babies' heads are large relative to our birth canals. This tight "fetopelvic" fit increases the risk of obstructed labor, which in turn has potentially dire outcomes for both mother and child. It has long been thought that bipedalism prevents further widening of the human pelvis. Evolutionary anthropologists from the University of Vienna and colleagues now present evidence for a different explanation, published in PNAS. A larger bony pelvic canal is disadvantageous for the pelvic floor's ability to support the fetus and the inner organs and predisposes to incontinence.