During pregnancy in the human, hormones such as relaxin allows the pelvic bones to be more flexible for delivery. The gap of the symphysis pubis, normally is 4–5 mm but during pregnancy there is an increase by at least 2–3 mm. The symphysis pubis separates to some degree during childbirth hence pubic symphysis is an amphiarthrodial joint.
Oxytocin is a peptide hormone secreted by the posterior pituitary. It is also a neuropeptide, used for inter-neuron communication. This hormone is responsible for secretion or ejection of milk. PRH or prolactin releasing hormone is responsible for the release of Prolactin or PRL, which is a hormone responsible for milk production. Progesterone inhibits lactation during pregnancy.