Friction between the foetal head and the cervix during labour.
D002584:Cervix Uteri / Q000502:physiology*; D005113:Extraction, Obstetrical; D005260:Female; D005333:Fetus; D006257:Head; D006801:Humans; D007746:Labor Presentation; D007743:Labor, Obstetric; D009119:Muscle Contraction; D009120:Muscle Cramp; D007744:Obstetric Labor Complications; D006831:Polyhydramnios; D011247:Pregnancy; D013035:Spasm