Changes

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Several hormones are known to exhibit an effect on the cervix resulting pre-parturition softening; 'prostaglandin' and 'relaxin'. Prostaglandin levels increase markedly in the days prior to parturition, peaking at parturition. There are two main types and sources of prostaglandin that are important in cervical softening; prostaglandin E2 (PGE2) and Prostaglandin F2α (PGF2α). PGF2α is produced in responce to the production of fetal corticoids and is produced by the placenta.

Several hormones are known to exhibit an effect on the cervix resulting in pre-parturition softening; 'prostaglandins' and 'relaxin'. Prostaglandin levels increase markedly in the days prior to parturition, peaking at parturition. There are three main types and sources of prostaglandin that are important in cervical softening; prostaglandin E2 (PGE2), prostacyclin (PGI2) and Prostaglandin F2α (PGF2α).  

PGF2α is produced by the placenta in responce to the production of fetal corticoids. (PGF2α also helps to remove the progesterone block pre-parturition.) PGF2α is not thought to act directly on the cervix and instead causes the myometrium of the uterus to become more active resulting in increased cervical stimulation and therefore softening and dilation. PGE2 is maternally derived and is the main driver of cervical softening. The production of PGE2 coincides with reductions in progesterone levels. PGE2 also acts on the uterus resulting in increased myometrial contractions, increased uterine pressure and therefore also cervical stimulation. PGI2

Relaxin is produced by the ovaries and the placenta and together with progesterone prevent uterine contractions throughout the pregnancy. However, relaxin also aids in the loosening of tissues in the cervix and pelvic ligaments to loosen pre-parturition. Relaxin and PGE2 work in combination on the cervix.