BIOL 221 Lecture Notes - Lecture 14: Breech Birth, Episiotomy, Uterine Contraction
4 Mar 2020
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Document Summary
Oxytocin stimulates uterine contraction and release of prostaglandins. Contractions push baby"s head against cervix causing cervix to stretch and efface (become thinner). Stimulation of receptors leads to afferent impulses to hypothalamus that stimulate release of more oxytocin by neurohypophysis. Dilation stage cervix dilates to ~ 10 cm (4 ) and effaces. Normally the opening of the cervix is very small. Dilation of the cervix normally takes 6-12 hours and enlarges the opening to about 10 cm (4 ). The initial contractions are of short duration and widely spaced. During this time contractions are long and closely spaced. Crowning occurs when the baby"s head shows. If the baby is in a breech position (buttocks first) or if it is in distress, then the fetus may need to be surgically removed in a procedure called a cesarean section. Sometimes the vagina begins to tear and a surgical cut called an episiotomy may be done to limit tearing of the vagina.
