Medical expert of the article
New publications
Anomalies of childbirth - Overview of information
Last reviewed: 08.07.2025
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Among the factors that complicate the birth process, the most important are the following: features of the mother's pelvis; features of the fetal presentation, as well as types of presentation; the strength of uterine contractions. The disproportion between the sizes of the fetal head and the mother's pelvis is due to an unfavorable combination of their diameters.
[ Mother's pelvis
The ideal pelvis has a rounded border of the upper part of the pelvic inlet (i.e. it has a gynecoid shape, typical for the female pelvic structure), but in almost 15% of women the border of the upper part of the pelvic inlet is elongated-oval (the so-called anthropoid shape - male-type pelvis). An excessively flat upper part of the pelvic inlet (the so-called flat pelvis) is observed in 5% of women whose height exceeds 152 cm, and in 30% of women whose height is less than 152 cm. With scoliosis, kyphosis of the spine, fusion of the sacrum with the 5th lumbar vertebra, spondylolisthesis and pelvic bone fractures, the anatomy of the mother's pelvis is disrupted. In the past, the most significant problems in women arose as a consequence of rickets and poliomyelitis. Pelvic stenosis should be suspected in cases where the presenting head has not been inserted in primiparous women of the Caucasian race by the 37th week of pregnancy.
Type of presentation
In the case of cephalic presentation, the less the head is bent, the less favorable the situation. In the case of transverse position and brow presentation, a cesarean section is necessary: in the case of face presentation and posterior occipital presentation, although delivery through the natural birth canal can occur, it is still more likely that obstacles will arise. Breech presentation is especially unfavorable (from the point of view of the prospect of difficult labor) if the fetus's body weight exceeds 3.5 kg.
Strength of uterine contractions
Uterine contractions start from the area of the fundus of the uterus and spread downwards. The intensity and duration of contractions are greatest in the area of the fundus of the uterus, but they reach their peak in all parts of the uterus simultaneously. Normal contractions should occur with a frequency of 3 times per 10 minutes, they last up to 75 seconds. At the height of the peak of contraction, the pressure should reach 30-60 mm Hg, while during periods of relaxation, the tone of the uterus should be maintained at a pressure of 10-15 mm Hg.
Disruption of uterine contractility
Contractions may be hypotonic (low uterine tone in the relaxation phase, weak contraction peaks), or normotonic but excessively rare. Such disturbances in uterine contractility are corrected (enhanced) with oxytocin. In other cases, the lower uterine segment is hyperactive, with the normal dominant role of the fundus absent and contractions may be directed upward from the lower segment. In such cases, the cervix does not open properly, and the mother experiences severe back pain and a desire to push even before the cervix has opened. In such situations, the mother should be provided with adequate analgesia; epidural anesthesia is particularly effective, since the irresistible desire to push is reduced (as with intravenous pethidine 25 mg).
Cervical dystocia
This term refers to a situation where a rigid, inelastic cervix does not open. Predisposing factors may include previous trauma, cicatricial process, cone biopsy and cauterization. It is often very difficult to determine why the cervix does not open: due to organic causes or as a result of uncoordinated labor. In both cases, it is usually necessary to resort to delivery by cesarean section.
Consequences of prolonged labor
Prolonged labor increases the risk of both neonatal mortality and maternal morbidity (primarily due to infectious complications). Modern methods of labor management provide constant monitoring of the labor process, thereby facilitating the task of recognizing delays in labor and timely correction of this complication.
In case of abnormalities in labor, one should promptly ask the question of how safe delivery through the natural birth canal is possible.