The accurate definition of cephalopelvic disproportion (CPD) is when a babies head or body is too large to fit through the mother’s pelvis. It is believed that true CPD is rare, but many cases of “failure to progress” during labor is given a diagnosis of CPD. When an accurate diagnosis of CPD has been made, the safest type of delivery for mother and baby is a cesarean delivery.
What causes cephalopelvic disporoprtion (CPD)?
The possible causes of cephalopelvic disproportion (CPD) include:
- Large baby due to:
- Hereditary factors
- Postmaturity (still pregnant after due date has passed)
- Multiparity (not the first pregnancy)
- Abnormal fetal positions
- Small Pelvis
- Abnormally shaped pelvis
How is cephalopelvic disproportion diagnosed (CPD)?
The diagnosis of cephalopelvic disproportion is often used when labor progress is not sufficient and medical therapy such as use of oxytocin is not successful or attempted. CPD can rarely be diagnosed before labor begins even if the baby is thought to be large or the mom’s pelvis is known to be small. During labor, the baby’s head molds and the pelvis joints spread, creating more room for the baby to pass through the pelvis. Ultrasounds are used to estimate fetal size, however they are not 100% accurate in determining fetal weight. A physical examination that measures pelvic size can often be the most accurate at determining a diagnosis of CPD. If a true diagnosis of CPD cannot be made, the use of oxytocin is often administered to see if this aides in labor progression or change in fetal positioning.
What about future pregnancies?
Cephalopelvic disproportion is a rare occurance. According to the American College of Nurse Midwives(ACNM), CPD occurs in 1 out of 250 pregnancies. If you have been diagnosed with CPD, this does not automatically mean that you will have this problem in future deliveries. According to a study published by the American Journal of Public Health, over 65 % of women who had been diagnosed with CPD in previous pregnancies, were able to deliver vaginally in subsequent pregnancies.
Compiled using information from the following sources:
Danforth’s Obstetrics and Gynecology Ninth Ed. Scott, James R., et al, Ch. 22.
American College of Nurse-Midwives, http://www.acnm.org/
American Pregnancy Association, http://www.americanpregnancy.org