From the Guidelines
Cephalopelvic disproportion (CPD) is a condition where the fetal head is too large to pass through the maternal pelvis, and its key findings include failure of the fetal head to engage in the pelvis, arrest of cervical dilation during active labor, and lack of fetal descent despite strong contractions, as evidenced by a recent study published in the American Journal of Obstetrics and Gynecology 1. The primary findings of CPD can be identified through a combination of physical examination, ultrasound assessment, and labor monitoring. Some of the key indicators of CPD include:
- Failure of the fetal head to engage in the pelvis despite adequate utine contractions
- Arrest of cervical dilation during active labor
- Lack of fetal descent despite strong contractions
- Abnormal pelvic architecture with reduced pelvic dimensions during clinical pelvimetry
- Large fetal head circumference relative to the maternal pelvic dimensions
- Significant molding and caput formation of the fetal head during labor Maternal risk factors that increase suspicion for CPD include:
- Short stature
- History of pelvic trauma or fracture
- Congenital pelvic abnormalities
- Previous cesarean delivery for CPD Fetal factors that contribute to CPD include:
- Macrosomia
- Abnormal fetal position (such as persistent occiput posterior)
- Certain congenital anomalies like hydrocephalus If evidence of CPD is found, cesarean delivery is typically indicated as vaginal delivery would be unsafe for both mother and baby, potentially leading to prolonged labor, maternal exhaustion, uterine rupture, birth trauma, or fetal distress, as supported by the recent study 1. In cases where CPD is suspected, a thorough cephalopelvimetric assessment is vital to exclude the presence of disproportion, and clinicians should err on the side of intervention by cesarean delivery in the presence of uncertainty about potential harm, as recommended by the study 1.
From the Research
Key Findings of Cephalopelvic Disproportion (CPD)
- Cephalopelvic disproportion (CPD) is a recognized obstetric problem with potential risk to both mother and infant 2.
- The most important anthropomorphic risk factors for CPD were maternal head circumference in relation to height and paternal head to height ratio 2.
- Primiparity was an important independent predictor of CPD, regardless of the mode of onset of labor 2.
- Fetal pelvic index was not a clinically useful tool to predict the mode of delivery for patients at high risk of CPD 3.
- Risk factors for CPD include fetal macrosomia, infertility treatment, previous caesarean delivery, maternal obesity, and polyhydramnios 4.
- Deliveries complicated by CPD resulted in a high rate of Caesarean delivery, laceration of the cervix, rupture of uterus, intrapartum mortality, and low 1-min Apgar scores 4.
- Maternal age and weight increased the risk for having CS due to CPD, while maternal height and the number of previous vaginal deliveries reduced the risk 5.
- The relative risk ratio for higher neonatal birthweight/maternal height index was significant for CS due to CPD and non-CPD CS 5.
Predictive Factors
- Maternal head circumference in relation to height and paternal head to height ratio were significant predictors of CPD 2.
- Fetal head circumference was not a predictor of CPD 2.
- Maternal or paternal shoe-size, induction of labor, and gestation at delivery were not predictors of CPD 2.
- Fetal pelvic index was not a useful predictor of CPD 3.
Perinatal Outcomes
- Deliveries complicated by CPD had higher rates of adverse perinatal outcomes, including laceration of the cervix, rupture of uterus, intrapartum mortality, and low 1-min Apgar scores 4.
- CPD was associated with a higher rate of Caesarean delivery 4.
- The risk of CPD was higher in mothers with a history of previous Caesarean delivery, infertility treatment, and maternal obesity 4.