Childbirth (also called labour, birth, partus or parturition) is the culmination of a or period with the delivery of one or more newborn from a 's . The process of human childbirth is categorized in 3 stages of labour. The first stage accomplishes the shortening and then the dilation of the cervix. It is deemed to have started when the cervix is 3 cm dilated, and ends with full dilation. Contractions begin in the first stage of labour although they may be irregular and sporadic at first. The second stage, often called the pushing stage, starts when the cervix is fully dilated and ends with the expulsion of the fetus. In the third stage, the detaches from the uterine wall and is expelled through the birth canal. Preceding the onset of labour is a period called the latent phase. This phase may last many days, and the contractions are an intensification of the that start around 26 weeks gestation. Latent phase ends with the onset of active first stage labour.
The mechanics of birth
Because humans are bipedal with an erect stance and humans have relatively the biggest head and shoulders to the size of the pelvis of any species, humans fetuses are adapted to make birth possible.
The erect posture causes the weight of the abdominal contents to thrust on the pelvic floor, a complex structure which must not only support this weight but allow three channels to pass through it: the urethra, the vagina and the rectum. The relatively large head and shoulders require a specific sequence of manoeuvres to occur for the bony head and shoulders to pass through the bony ring of the pelvis. If these manoeuvres fail, the progress of labour is arrested. All changes in the soft tissues of the cervix and the birth canal are entirely dependent on the successful completion of these six maneuvers:
Engagement of the fetal head in the transverse position. The baby is looking across the pelvis at one or other of the mother's hips.
Descent and of the fetal head
Internal rotation. The fetal head rotates 90 degrees to the so that the baby's face is towards the mother's rectum.
Delivery by extension. The fetal head passes out of the birth canal. Its head is tilted backwards so that its forehead leads the way through the vagina.
Restitution. The fetal head turns through 45 degrees to restore its normal relationship with the shoulders, which are still at an angle.
External rotation. The shoulders repeat the corkscrew movements of the head, which can be seen in the final movements of the fetal head.
These movements are all due to the relationship of the bony head and shoulders of the fetus to the bony ring of the mother's pelvis and are independent of any changes in the maternal soft tissues.
The stages of normal human birth
The latent phase of labour causes confusion with many. Latent phase may last many days and the contractions are an intensification of the contractions that start around 26 weeks gestation. occurs during the closing weeks of pregnancy and is usually complete or near complete, by the end of latent phase. Cervical effacement is the incorporation of the cervix to form the lower segment of the uterus. The muscular portion of the uterus is the upper segment, and is made of . The lower segment of the uterus has no muscles and is comprised of the cervix itself, which becomes massively stretched and thinned out. This cervical effacement will usually be accomplished fully prior to the onset of labour. The degree of may be felt during a vaginal examination. A 'long' cervix implies that not much has been taken into the lower segment, and vice versa for a 'short' cervix. Latent phase ends with the onset of active first stage; when the cervix is about 3 cm dilated.
Mother and newborn with still attached after a
First stage: contractions
The first stage of labor is an active stage and should not be confused with the latent phase of labor.
The first stage of labor starts classically when the effaced cervix is 3 cm dilated.