In the last weeks of pregnancy in a woman with a narrow pelvis, deviations from the physiological course of pregnancy are often noted. So, in primiparous there is a genital, and in multiparous – a drooping belly. This anomaly further prevents the correct insertion of the fetal head and adversely affects the development of labor.
A frequent complication — incorrect position and presentation of the fetus due to a mismatch in the size of the head and entry into the pelvis — is observed about 4 times more often than with normal pelvis. In particular, a narrow, especially flat pelvis will create the prerequisites for the formation of extensor prepositions .
The next deviation from the normal course of childbirth is premature and early discharge of amniotic fluid (5 times more often than with a normal pelvis), which is sometimes accompanied by the extrusion of the umbilical cord and small parts of the fetus. These complications are explained by the mobility of the fetal head for a long time, the absence of a “contact belt” and, as a result, the presence of communication between the front and back waters, which exert more than normal pressure on the amniotic fluid.
Due to the absence of the fetal bladder, there are no conditions that normally contribute to smoothing and opening the neck; therefore, in spite of a strong labor activity, labor is slow and inferior. In this regard, the following can be observed: a) a prolonged course of the first period of childbirth; b) ascending infection; c) exhaustion of the nervous system of the woman in labor and her physical fatigue; d) secondary weakness of labor (about 1/6 of all women in labor with a narrow pelvis, that is, 3-4 times more often than women with a normal pelvis); e) sharply painful, convulsive contractions and a tetanic state of the uterine muscles as a result of excessive, continuous irritation of the uterine receptors with long-standing waters and continuously increasing compression of the soft tissues of the birth canal. With such convulsive contractions, the opening of the cervix does not progress. Due to prolonged pressing of an unstressed cervix to the bones of the pelvis , edema of the anterior lip of the cervix often occurs between the head of the fetus and the pubic joint of the pelvis; sometimes there is a danger of rupture of the uterus or its separation from the arches; f) fetal asphyxiation due to a violation of the uteroplacental circulation, due to abnormal, convulsive contractions and the tetanic state of the uterus; intracranial injury to the fetus; g) rupture of the pubic joint with damage to the bladder, sometimes symphysitis ; h) atonic bleeding in the subsequent and early postpartum periods due to overstrain and secondary weakening of contractility and loss of uterine tone, the onset of infection and the development of septic endometritis, the development of afibripogenemia ; i) stillbirth, which in women with a narrow pelvis ranges from 3.88 to 9.5%.