Vaginal delivery is considered the natural method of birth of a baby through the birth canal (cervix and vagina). Ideally, spontaneous contractions set in after 40 weeks of gestational age. At this point, the cervix is fully dilated and the woman feels the urge to push until the expulsion of the child. [1] [2]

A normal delivery comprises three stages:

Latent phase
In the pre-labor phase the woman perceives regular uterine contractions. At this point, the cervical dilation begins and the water breaks. The uterine cavity starts to tighten, the upper segment of the uterus shortens and the pressure on the fetus increases. Full dilation is reached when the cervix has widened around 10cm to allow passage of the baby's head. The expulsion stage begins. [3] [4]

The contractions (of the uterus) are stimulated by an increase of estrogen and the neurotransmitters prostaglandin and oxytocin. [5] While first contractions may start around 26 weeks gestation and are relatively painless, strong labor pains push the child through the birth canal. [6]

Expulsion phase
The expulsion stage begins when the cervix is fully dilated, and ends when the baby is born. At the beginning of the normal second stage, the fetal head is fully engaged in the pelvis; the widest diameter of the head has passed below the level of the pelvic inlet. The fetal head then continues descent into the pelvis, below the pubic arch and out through the vaginal opening. This is assisted by the additional maternal efforts of "bearing down" or pushing. [3] [4] [6]

First, the fetal head is in the transverse position and is facing across the pelvis at one of the mother's hips. Then, the fetal head descends, flexes and rotates 90 degrees to the occipito-anterior position so that the baby's face is towards the mother's rectum. The baby passes out of the birth canal with its head tilted forwards so that the crown of its head leads the way through the vagina. The fetal head turns through 45 degrees to restore its normal relationship with the shoulders, which are still at an angle. The shoulders repeat the corkscrew movements of the head, which can be seen in the final movements of the fetal head. Once, the head and shoulders are born, the main part of delivery is done. Optimally, the small body easily slides out. [3] [4]

In case the birth canal is too tight for the fetal head, an episiotomy is done in order to widen the vaginal opening. In earlier times, episiotomies were a common practice to accelerate the process. Current guidelines suggest letting the tissue rupture and only conduct an episiotomy in case of emergency. [7] [8] [PERINEUM]

Involution stage
The third stage of labor is the period from just after the fetus is expelled until just after the placenta is expelled. Placental expulsion begins as a physiological separation from the wall of the uterus. Bleedings help in this process; up to 300 ml of blood loss is normal. Together with the umbilical cord, the placenta and the amniotic cauls leave the vagina. [2] [3] [4]

Natural birth?
Vaginal delivery is usually done in a hospital with the mother lying on her back. The pains can be mitigated by pharmaceutical pain control like regional anesthetics epidurals (EDA), and spinal anaesthesia. A standard procedure is the constant monitoring of the baby's heartbeat as well as the half-hourly blood pressure and pulse rate reading of the mother. [1] [2]

Many experts criticize the dogmatic obedience of supposedly necessary precautions (surveillance of mother and unborn) because it causes more stress for the mother and her child and makes birth unnatural. [1] According to the English gynecologist Grantly Dick-Read (1890-1959) the labor pain hardly existed among indigenous people. [9] The US-American midwife and author Ina May Gaskin (1940) is convinced that the stress and fear of the pain causes the pain itself. In international lectures and workshops she tells about counterexamples. [10]

Other scientists have developed alternatives to a traditional delivery such as "the gentle birth" by the French gynaecologist, obstetrician and author Frédérick Leboyer, "the painless birth" by the French doctor Fernand Lamaze (1891-1957), and the "hypnobirthing method" by Marie F. Mongan. All methods focus on the attention to the wellbeing of mother and child and to birth as a magical event between newborn and its mother. [9]

Further Links:
TEDx Talks, Reducing fear of birth in U.S. culture: Ina May Gaskin at TEDxSacramento, 2013 (YouTube)
Earth Birth Method (Website)