Cephalopelvic Disproportion: Symptoms, Types, Causes and Treatment

Cephalopelvic disproportion (CPD) is a significant obstetric challenge encountered during labor and delivery. It occurs when the size or shape of the fetal head is mismatched with the maternal pelvis, preventing a safe vaginal delivery. This article explores CPD through its symptoms, types, causes, and treatment options, synthesizing modern research and clinical observations to provide a thorough understanding for patients, families, and healthcare professionals.

Symptoms of Cephalopelvic Disproportion

Recognizing the symptoms of CPD is essential for timely intervention and prevention of complications for both mother and baby. CPD often reveals itself during labor, making ongoing monitoring and prompt assessment critical.

Symptom	Description	Clinical Context	Source(s)
Labor Arrest	Labor fails to progress as expected	Persistent cervical dilation or descent stalls	3 6 8 9
Prolonged Labor	Labor lasts significantly longer	Slow progress despite adequate contractions	3 6 8 9
Fetal Distress	Signs of fetal compromise	Abnormal fetal heart rate patterns	9
Maternal Exhaustion	Extreme fatigue or distress	Due to prolonged or obstructed labor	9

Table 1: Key Symptoms

Labor Arrest and Prolonged Labor

The most common clinical clue to CPD is a lack of labor progress, even when uterine contractions are strong and regular. This “failure to progress” can occur during the active phase of labor, characterized by the cervix ceasing to dilate or the fetal head failing to descend through the birth canal despite adequate contractions 3 6 8.

Fetal Distress

When labor is obstructed, the fetus may experience distress, often first noticed as an abnormal heart rate pattern on fetal monitoring. Prolonged or obstructed labor increases the risk of hypoxia and other complications for the baby 9.

Maternal Exhaustion and Complications

Prolonged labor due to CPD can lead to maternal exhaustion, dehydration, and increased risk of infection. Without timely management, further complications such as uterine rupture or fistula formation may occur 9 13.

Clinical Signs and Monitoring

Modern labor monitoring, including electronic fetal monitoring and assessment of contraction patterns, can help identify dysfunctional labor associated with CPD. Uterine contractions in CPD may show a distinctive shape—rapid rise with a slower return to baseline—suggesting a physiologic adaptation to the mechanical obstruction 6.

Types of Cephalopelvic Disproportion

Understanding the different types of CPD helps clinicians tailor interventions and anticipate challenges during labor.

Type	Description	Diagnostic Feature	Source(s)
Inlet CPD	Disproportion at pelvic entry	Fetal head cannot enter pelvis	5 11 3
Midpelvic CPD	Disproportion at pelvic midsection	Obstruction as head descends	5 3
Outlet CPD	Disproportion at pelvic exit	Fetal head arrested at outlet	5 3
Borderline CPD	Minimal mismatch, may allow vaginal birth	Slight excess head over inlet capacity	5

Table 2: Types of Cephalopelvic Disproportion

Inlet Disproportion

Inlet CPD occurs when the fetal head is too large to enter the pelvic brim. This typically results from a small or abnormally shaped pelvic inlet or an unusually large fetal head 5 11. Labor fails to progress from the beginning, and vaginal delivery is unlikely unless interventions are made.

Midpelvic Disproportion

Midpelvic CPD refers to obstruction happening midway through the pelvis. Here, the fetal head may enter the pelvis but becomes stuck as it moves downward. This type can be more challenging to diagnose before labor and may only become apparent as labor fails to progress further 5.

Outlet Disproportion

Outlet CPD happens at the final portion of the birth canal. The fetal head may have descended but cannot pass through the pelvic outlet, possibly due to a narrow pubic arch or soft tissue obstruction 5 3.

Borderline Disproportion

Some cases are classified as "borderline," where the mismatch is minimal. These cases may still result in vaginal delivery, particularly with skilled obstetric management, but carry an increased risk of labor complications 5.

Pelvic Shapes and Implications

Four basic pelvic shapes—gynecoid, android, anthropoid, and platypelloid—also influence the likelihood and type of CPD encountered. Gynecoid pelves are most favorable for childbirth, while android and platypelloid shapes are more prone to disproportion 3.

Causes of Cephalopelvic Disproportion

CPD can be the result of maternal, fetal, or combined factors. Understanding these can help with prevention strategies and management planning.

Cause	Description	Risk Factors or Examples	Source(s)
Maternal Pelvic Size/Shape	Small or abnormally shaped pelvis	Short stature, pelvic deformity	8 3 12
Fetal Size	Large baby relative to pelvis	Macrosomia, post-term pregnancy	8 3 7
Fetal Position	Malposition increases effective head size	Occiput posterior/transverse	3 1
Maternal Conditions	Factors affecting pelvic growth/shape	Rickets, malnutrition, trauma	12 8

Table 3: Causes of Cephalopelvic Disproportion

Maternal Pelvic Factors

A small or abnormally shaped pelvis is one of the primary maternal causes of CPD. Short maternal stature is strongly associated with increased risk; women under 150 cm tall are up to three times more likely to experience CPD 8. Pelvic abnormalities may result from childhood rickets, malnutrition, or prior pelvic trauma 12.

Fetal Factors

Large babies (macrosomia), especially those weighing 4,000 grams (approx. 8.8 lbs) or more, are a leading fetal cause of CPD 8. Post-term pregnancies and certain genetic conditions can also result in increased fetal head or body size 3 7.

Fetal Position and Presentation

Malposition of the fetal head, such as occiput posterior or transverse positions, can increase the effective diameter of the presenting part, exacerbating or mimicking CPD even when actual sizes are compatible 3 1.

Combined and Uncommon Causes

Occasionally, CPD results from rare conditions such as a retained lithopedion (calcified fetal remains) or soft tissue masses in the pelvis, which create a mechanical obstruction 7.

Risk Factor Summary

• Maternal height and pelvic size
• Fetal size (macrosomia)
• Fetal malposition
• Maternal malnutrition or skeletal disease
• History of pelvic trauma or deformity

Treatment of Cephalopelvic Disproportion

Timely and effective management of CPD is vital for maternal and neonatal safety. Treatment depends on severity, type, and clinical context.

Treatment	Description	Indications	Source(s)
Cesarean Section	Surgical delivery of the baby	Confirmed/probable CPD, failed labor	10 8 12
Symphysiotomy	Surgical widening of pelvic joint	Selected mild cases, limited resources	2 10
Forceps/Vacuum	Assisted vaginal delivery	Borderline CPD, fetal head low in birth canal	12
Craniotomy	Decompression of fetal head	Obstructed labor, non-viable fetus	12

Table 4: Treatment Options

Cesarean Section

The most common and reliable treatment for significant CPD is cesarean section (C-section). This surgical approach is indicated when CPD is diagnosed before or during labor, especially when labor fails to progress or there are signs of fetal or maternal distress 8 10 12. Modern obstetric practice favors timely C-section to reduce complications.

Symphysiotomy

In selected mild cases of CPD, especially where C-section is unavailable or not feasible (such as in some low-resource settings), symphysiotomy—a surgical procedure that widens the pelvic joint—may be considered. This allows some women to deliver vaginally, though it is less commonly used today due to potential complications 2 10.

Assisted Vaginal Delivery

In cases of borderline CPD where the fetal head is low in the pelvis and no significant distress is present, forceps or vacuum extraction may be attempted. This approach requires careful selection to avoid complications 12.

Craniotomy

When the fetus is non-viable or has already died, and labor is severely obstructed, craniotomy (surgical reduction of fetal skull size) may be employed as a last resort to prevent maternal morbidity or mortality. This is now rare in modern obstetric practice due to improved prenatal care and access to C-section 12.

Supportive and Preventive Measures

• Early and accurate diagnosis: Clinical assessment and monitoring during labor are key to identifying CPD early 3 6.
• Antenatal care: Nutritional support and management of maternal health may reduce risk in at-risk women 9 8.
• Prompt referral: Timely referral to specialist care improves outcomes, especially in resource-limited settings 12 9.
• Antibiotics and supportive care: To reduce infection risk in prolonged or obstructed labor 9.

Conclusion

Cephalopelvic disproportion remains a significant cause of labor complications worldwide. With appropriate recognition, classification, and management, most adverse outcomes can be prevented.

Key points covered:

• Symptoms of CPD include labor arrest, prolonged labor, fetal distress, and maternal exhaustion, often identified during labor 3 6 8 9.
• Types of CPD are classified by the pelvic level involved (inlet, midpelvic, outlet, or borderline), and pelvic shape plays a crucial role 5 3.
• Causes are multifactorial, involving maternal pelvic size/shape, fetal size, fetal position, and rarely, other mechanical factors 8 3 12 7.
• Treatment options include C-section, symphysiotomy, assisted vaginal delivery, and in rare cases, destructive procedures, with prevention and early intervention being vital 10 8 12 2.

Through awareness, skilled assessment, and timely intervention, both mothers and babies facing CPD can achieve the best possible outcomes.