Experimental evidence for the progress of labor with the increase in the force of cervical dilatation after rupture of the membranes.
To examine the mechanical forces involved in cervical distention, actual tensions of the fetal membranes up to the bursting level were measured experimentally with the use of five circular membrane holders that simulate various cervical dilatations (radii 1 to 5 cm). The results show that the force of cervical dilatation with the head alone increases remarkably as the cervix dilates, and this force is always larger than that when the membranes are intact. Thus the membranes appear to interfere with effective cervical dilatation and progress of labor after fixation of the fetal head to the cervix.
D002584:Cervix Uteri / Q000502:physiology*; D005321:Extraembryonic Membranes; D005260:Female; D006801:Humans; D007743:Labor, Obstetric; D008954:Models, Biological; D011247:Pregnancy; D011312:Pressure; D013314:Stress, Mechanical; D014590:Uterine Contraction