Cephalopelvic Disproportion

When you're pregnant, it's normal to be a little nervous about labor and delivery, especially if it’s your first baby. It can be scary, and you might start to think about all the things that can go wrong. A common worry is that the baby will be too big or get stuck. But what are the chances that could really happen?

Cephalopelvic disproportion (CPD) is a medical issue that can arise during childbirth. It occurs when a baby is having trouble getting through the birth canal. The baby may be very large or in a difficult delivery position, or the mom’s pelvis may be too small for the baby to pass safely. Here’s what you need to know about CPD, including how often this delivery complication happens, the risks, and how doctors treat it.

How Often It Occurs

True cephalopelvic disproportion is when the size of the baby’s head and the mom’s pelvis are mismatched, so it is difficult or impossible for the baby to get through. It is very rare. However, other issues, such as the position of the baby’s body or head inside the womb, can cause labor to progress slowly or stop progressing. These complications can also lead to obstructed labor and are all sometimes considered CPD, as well. 

Large Babies 

Most women, including petite moms, can safely deliver a baby even if the doctors believe the baby might be big. The pelvis is flexible to accommodate birth, and the bones in the baby's head are designed to change shape for delivery. So, if your doctor tells you that your baby measures large, here are a few things to keep in mind: 

Measurements Are Not Always Right

The doctors cannot weigh your baby or know the exact size of his head while he's still inside your body. Ultrasound is an excellent tool, and it can give the doctor a good idea of what to expect, but it's still just an estimate. It is not uncommon for a baby who appears big to be born at an average weight. 

However, if a mom has a pelvic injury or a genetic issue that makes the pelvis narrow, or the baby's position for delivery is not ideal, CPD can become an issue.

Risk Factors

While cephalopelvic disproportion is not common, some situations and conditions could put you at a higher risk for encountering it. Here are the risk factors for CPD. 

For the Baby

• Size. When a baby is much bigger than average, so is his head. The risk of CPD goes up when the baby is over 8 lbs 13 oz (4000 g), and it’s even higher when the baby is over 9 lbs 15 oz (4500 g).
• Position. If the baby is breech or lying sideways, it will affect labor and delivery.
• Presentation. Delivery is easier when the smallest part of the head (occiput anterior) leads the way. But, when a larger part of the baby’s head such as the forehead or face is heading out first, it can be a little more challenging to make it through the pelvis.
• Health. Certain health conditions in the baby, such as hydrocephalus, can cause the baby’s head to be larger than average. 
• Gender. Boys tend to be larger than girls, so the risk of CPD with boys is a little higher.

For the Mother

• A history of pelvic surgery or injury  
• A pelvis that is narrow or has a genetic variation in shape
• First pregnancy 
• Diabetes and gestational diabetes 
• Polyhydramnios
• Obesity
• Malnutrition
• History of fertility treatments
• Going past the due date
• A previous c-section
• A short stature 
• Hispanic heritage
• Teen pregnancy where the pelvic bones have not fully grown

Diagnosis

CPD is usually diagnosed during labor when the baby is not progressing naturally through the birth process.

The doctor will suspect CPD if: 

• The labor is prolonged or lasting longer than expected.
• Uterine contractions are not strong enough to keep the labor moving forward.
• The thinning and dilation of the cervix is happening slowly or not at all.  
• The baby’s head is not engaging or entering the pelvis. 
• The baby is not moving down through the pelvic stations.

Can It Be Prevented?

Since cephalopelvic disproportion is not usually diagnosed until there is a problem during labor, it is difficult to prevent. However, your doctor will examine you and monitor your baby during your pregnancy. If the doctor suspects that CPD could be an issue, she will discuss it with you along with your options. The doctor will evaluate you for CPD by:

• Taking a health history, including your family history, and any surgeries or injuries you may have had.
• Examining your pelvis for its general size and shape.
• Using ultrasound results and physical exams to estimate the size of your baby.
• Monitoring the baby’s position inside the womb.

If you’ve already experienced CPD during a previous delivery, the doctors will be better prepared to make a delivery plan with you to prevent any complications during your next delivery. 

Treatment

The treatment for CPD is to continue with labor or move on to a cesarean section. The goal of treatment is to have a safe delivery, so the doctors will decide how to treat the condition based on how the delivery is going. 

Trial of Labor

When there is a possibility of CPD, the doctors may decide to let you try to labor. If your labor is moving along well, it may continue along with: 

• Close monitoring of your contractions, dilation, and the baby's progression down the birth canal.
• Close monitoring of the baby's movements and heart rate.
• Confirmation of the baby's position with a vaginal exam.
• Other tests such as X-ray, ultrasound, or MRI to visualize the baby's head and your pelvis.

During the trial of labor, you can help to open your pelvis and move the labor along by changing positions with the help of your nurse, doula, or partner. You can try: 

• Sitting
• Squatting
• Changing sides
• Going on your hands and knees 

If labor continues, forceps or a vacuum may be needed to help deliver the baby. But, if problems arise such as ineffective contractions, slow dilation and effacement, no descent, or fetal distress, the doctors will end the trial, and a c-section will be necessary. 

Cesarean Section

When the labor is very long, not progressing as it should, or causing complications for you or the baby, the next step is a c-section. 

You may need a c-section if: 

• You have had a previous c-section.
• You are an older first-time mom. 
• The baby is not in a good position for delivery. 
• The baby is overdue by a week or more.
• You are having complications such as pre-eclampsia.
• You or the baby are having other medical issues.

If you've already been through a pregnancy and had a difficult labor or a c-section due to CPD, the standard treatment for the next pregnancy is an elective c-section. The c-section should be scheduled when your baby is as close to full-term as possible. If the doctor is not sure of the dates, you may have to wait until your labor begins to have the c-section to prevent the problems associated with prematurity.

Complications

CPD is uncommon, and complications are even rarer. But, when a baby is too big to get through the mom’s pelvis or labor is very long and obstructed, it can lead to delivery problems and birth injuries. Some of the complications of cephalopelvic disproportion are: 

• Premature rupture of membranes 
• Dystocia
• Extreme molding of the head
• Umbilical cord prolapse
• Fetal distress
• Damage to the mom's perineum
• Injury to the baby’s head
• Uterine rupture
• Cesarean birth 

A Word From Verywell

As long as women continue to have babies, they will worry about labor and delivery. The good news is that human women have been getting through childbirth safely for over a million years. So, try to remember that labor and delivery is a natural process, and most children are born without any problems.

Thankfully, encountering cephalopelvic disproportion during delivery is rare. But, it's still normal to be a little anxious about it, especially if the doctors told you that your baby might be big. So, if you are very nervous, you can talk to your doctor about your concerns and learn as much as you can about delivering a big baby. The thought of CPD is scary, and if it does happen during delivery, your birth experience may change to include forceps, a vacuum, or a c-section. However, it doesn't mean that you and your baby won't still be healthy and safe.