CPD is a condition where the baby’s head or body has been determined to be too large to deliver vaginally, as it likely won’t fit through the mother’s pelvis. Many times CPD is diagnosed simply when labor is not progressing, but sometimes during an ultrasound a true diagnosis of CPD will be made, which means that a cesarean delivery will be required.

Likely Causes of CPD

There are many different possible causes of CPD, such as:

  • Large baby due to diabetes, genetic factors, overdue pregnancy or the mother’s second or more pregnancy
  • Breech or other abnormal fetal positioning
  • Smaller than normal, or abnormally shaped pelvis

Diagnosis of CPD

In most cases CPD is diagnosed during labor when there is a lack of progress, and the use of oxytocin to help labor along either does not yield results or cannot be attempted. It is unusual for CPD to be diagnosed prior to labor, as changes in the baby’s size and flexibility of the mother’s pelvis is impossible to estimate. On occasion a late stage ultrasound can be performed to judge the approximate size of the baby, but again it is not always accurate and doesn’t account for physical changes during labor.

 As labor progresses the skull plates in the baby’s head will mold and the joints in the pelvis will spread to create more space for the baby to pass through. If labor begins to slow or the contractions are not making progress then oxytocin may be administered in order to help it along.

During labor a physical examination and measurement of the pelvis can be made to determine if CPD is a factor, in which case a cesarean delivery will be performed.

CPD and Future Pregnancies

True CPD is quite rare, and is diagnosed in only 1 of 250 pregnancies. Studies show that there is a 65% chance that a mother who previously had a diagnosis of CPD will be able to deliver vaginally in her next pregnancy. (See VBAC for more information).