The biomechanism of childbirth is a wholevarious movements that the fetus passing through the birth can do. These movements are directly related to the structure of the female pelvis. They consist in bending / unbending the child's head, turning it around the axis, lateral declination of the fetal head and pendulum movements aimed at its progress along the birth canal.
All these movements are provided by the dimensions andthe shape of the pelvis of a woman, the presence of amniotic fluid in sufficient quantity, a cheese-like lubricant, which covers the child's body, reducing friction, as well as the size and shape of the fetal head. In addition, the biomechanism of labor is provided by the activity of the uterus, more precisely, by its contractions. This creates forward movements for the advancement of the fetus along the maternal pathways. An additional factor that contributes to the reduction of the uterus is its ligamentous apparatus. In this case, the circular ligaments pull the uterine bottom from the front, and the sacral-uterine ligaments are held, not allowing to deviate, and fix it at the surface of the sacrum.
Biomechanism of labor with fetal presentation(occipital) consists of the following moments: flexion of the head and its smooth lowering into the cavity of the small pelvis. When bending the head, the leading point is determined - a small fontanelle that approaches the wireline of the pelvis. It is this point that appears the first of the sex slit. The fetal chin at the same time tends to the chest. In the beginning the head changes its configuration. Further, when moving from the wide to the narrow part of the small pelvis, it makes a coup. After that the face is directed to the sacrum, and the neck to the symphysis. And in conclusion, the head extends and it leaves the plane of the pelvis - a forehead, a face and the last chin are born. After birth, the head assumes its original position. Then the hangers are born and the fetus is completely expelled.
Biomechanism of labor with pelvic presentation alsoconsists of rotational and translational movements, only in this case the fetus passes forward along the ancestral ways. The main reference point is the interverty gluteal line. The following are the moments that make up the biomechanism of labor: the buttocks are inserted into the small pelvis and move along it, the spine of the fetus makes a lateral bend, after which the trunk and humeral girdle are born. Folding of the fetal head and its internal rotation occur almost simultaneously. The head is born in a bent position.
Biomechanism of childbirth with leg presentation is similarthe one that is observed with the gluteal. Often after the passage of all amniotic fluid and with still incomplete opening of the cervix, the anterior leg may fall and even fall out of the vagina. This significantly complicates and delays the course of childbirth. After the cervix is fully opened, immediately behind the foot there are buttocks and so on according to the above biomechanism of labor.
As can be seen, the biomechanism of natural births depends on the position of the fetus and the location of the wired point.