Cephalopelvic disproportion is a birth complication that sometimes results in a cesarean section. It happens when the infant head is larger than the opening to the pelvis so that the baby cannot pass through the birth canal. Often, the mother has labored for a long time and gets to the point of pushing the baby out but cannot do so. It is a hard time for mothers and babies, and means making the decision to abandon the hard work of a delivery in favor of a surgical outcome. Sometimes the diagnosis can be made sooner, such as the situation where labor fails to allow the infant head to pass into the pelvic inlet.
Cephalopelvic disproportion can be dangerous to the baby, especially if a cesarean section is unavailable. The labor just keeps going on and eventually there is fetal distress that cannot be managed by a normal delivery. A baby can die from fetal distress secondary to cephalopelvic disproportion.
Cephalopelvic disproportion can be absolute or relative. In absolute cephalopelvic disproportion, there is something wrong with the pelvis that prevents normal delivery. This can include having had a severe injury to the pelvis in the past that has made the pelvic inlet or outlet abnormal. It can occur if the woman has been severely malnourished as a child and suffered from rickets.
Relative cephalopelvic disproportion means that the situation is right to have the baby's head get stuck but it is a situation that doesn't necessarily mean that it would happen in the future. The actual name for this situation is fetopelvic disproportion and means that the infant cannot navigate the birth canal in the position the baby is in. The baby may have its head straight or tilted in the posterior position-not flexed like it would normally be. The head of the baby may be tilted to one side and be asynclitic. The baby may be facing anteriorly (occiput posterior), which is more difficult to navigate. The end result is an arrest of labor and the baby's head stuck in the birth canal.
Cephalopelvic disproportion can occur from a misaligned pelvis in the mother. Chiropractic treatments can sometimes help that problem. In addition, if the mother is not allowed to walk around during labor, the pelvis can become rigid and can cause cephalopelvic disproportion. Sometimes breaking the bag of waters too early means that the fetal head drops into the pelvis in an abnormal position, resulting in a misfit between the head and the pelvis.
In a normal birth, the pelvis is flexible and opens up as part of the birth. If the pelvis isn't able to open gradually during the birth process, it can remain relatively closed and unable to allow for the passage of the fetus.
The treatment of cephalopelvic disproportion is a cesarean section. It is done as soon as the diagnosis of cephalopelvic disproportion is made or if there is fetal distress, whichever comes first. A cesarean section will pull out the baby from the pelvis and deliver it through the abdominal wall.
Just because a woman has cephalopelvic disproportion in one pregnancy doesn't mean it will happen again and it is a mistake to go straight to a cesarean section in subsequent births. Babies go through the birth canal differently and also are of different sizes. If a baby is expected to be bigger than a previous baby with cephalopelvic disproportion, a cesarean section may be the only option.
Doctors can do pelvimetry readings, which are x-ray estimates of the size of the pelvis. Pelvimetry might be able to tell if a pelvis is abnormally small or disfigured. Remember that the pelvis opens up during delivery so a small pelvis on pelvimetry doesn't necessarily mean the baby won't fit through the birth canal.