How do female mammals give birth?

Parturition, also known as childbirth, is the process by which the fetus is delivered from the uterus through the birth canal to the outside world. Parturition is triggered by a complex interplay of hormonal, biochemical, and mechanical factors.

The specific process of parturition varies among different species of female mammals, but the general sequence of events is as follows:

1. Onset of labor: The onset of labor is marked by the onset of regular and increasingly intense uterine contractions. These contractions are caused by the release of the hormone oxytocin from the posterior pituitary gland.

2. Dilation of the cervix: As the uterine contractions become stronger and more frequent, the cervix (the opening of the uterus) begins to dilate to allow the passage of the fetus.

3. Rupture of the amniotic sac: The amniotic sac, which is the fluid-filled sac surrounding the fetus, usually ruptures during labor. The rupture of the amniotic sac is commonly known as "breaking of water."

4. Descent of the fetus: As the uterine contractions continue, the fetus descends through the birth canal. The fetus may rotate during descent to be in the optimal position for delivery.

5. Delivery of the fetus: The fetus is delivered from the vagina as a result of maternal pushing efforts and the continued uterine contractions. The head of the fetus is usually delivered first, followed by the shoulders and the rest of the body.

6. Delivery of the placenta: After the fetus is delivered, the placenta (the organ that provides oxygen and nutrients to the fetus during pregnancy) separates from the wall of the uterus and is expelled from the vagina.

The process of parturition can vary in duration and intensity depending on several factors, including the species of mammal, the size and position of the fetus, and the overall health and fitness of the mother. In some cases, medical interventions, such as cesarean section, may be necessary if vaginal delivery is not possible or safe.