How does oxytocin help cause uterine contractions during childbirth?

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Hormone Many important physiological functions of vertebrates are controlled by steroid hormones.

Oxytocin facilitates uterine contractions during labor by binding to specific receptors located on the smooth-muscle cells of the uterus.1

As a pregnancy reaches term, the number of these oxytocin receptors increases significantly, which markedly enhances the uterus's sensitivity to the hormone. During the process of fetal expulsion, the posterior pituitary gland releases oxytocin in pulses into the bloodstream. Additionally, intrauterine tissues can secrete oxytocin locally, suggesting that paracrine signaling also plays a role in stimulating these contractions.1

While oxytocin acts as a powerful facilitator of the labor process—and is often used clinically to induce or strengthen labor—it is not strictly essential for parturition, as individuals with dysfunctional pituitary glands can still experience normal labor.1