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disproportion(dis?pro-por'shon) [ ¹dis- + proportion]
cephalopelvic disproportionAbbreviation: CPD
fetopelvic disproportionCephalopelvic disproportion.
|Mean LOS:||3.3 days|
|Description:||MEDICAL: Vaginal Delivery With Complicating Diagnoses|
Fetopelvic disproportion (FPD) refers to the inability of the fetal head to pass through the maternal pelvis; it occurs in 1% to 3% of all primigravidas. The size differential can be related to pelvic capacity or fetal factors. In absolute FPD, the fetal head is too large for the maternal pelvis so that vaginal birth cannot be safely achieved and cesarean delivery is required. Normally, the fetus delivers in the occiput-anterior position, assuming a flexed attitude, and with a suboccipitobregmatic diameter of 9.5 cm. If the fetal head takes other positions (occiput-posterior, brow), the delivering diameter of the head is larger, with a size of 11.5 cm and 13.5 cm, respectively. Most fetuses presenting with this larger diameter will not fit through the maternal pelvis.
Any contraction of the pelvis will impede the passage of the fetus through the birth canal. The maternal pelvis can be contracted at the inlet (defined as a diagonal conjugate of < 11.5 cm), at midpelvis (defined as < 15.5 cm; the sum of the interischial spinous and posterior sagittal diameters of the midpelvis), or at the pelvic outlet (defined as an interischial tuberous diameter of 8 cm or less). In relative FPD, the fetus may be delivered vaginally if a favorable combination of other factors can be achieved, including efficient uterine contractions; favorable fetal attitude, presentation, and position; maximization of maternal pelvic diameters; adequate molding of the fetal head; adequate expulsive efforts by the mother; and adequate stretching of maternal soft tissues.
FPD can lead to prolonged labor, with delayed engagement of the fetal head in the pelvis and increased risk of umbilical cord prolapse. Prolonged labor can place the mother at risk for dysfunctional uterine contractions, fluid and electrolyte imbalance, exhaustion, hypoglycemia, uterine rupture, need for operative delivery, and postpartum hemorrhage. Risks to the fetus include hypoxia, hypoglycemia, acidemia, and infection. Vaginal delivery may be difficult in these patients, with increased risk of maternal vaginal, cervical, and perineal lacerations; fractured sacrum or coccyx; fetal birth asphyxia; shoulder dystocia (difficult delivery because of fetal shoulder position); and traumatic birth injuries, especially cervical spine, nerve, clavicle, and cranial injuries. Some women who experience FPD that resulted in a cesarean delivery with one infant are able to deliver a subsequent infant vaginally.
The cause of FPD can be attributed to maternal and fetal factors. Maternal factors include inability of the pelvic soft tissues to stretch adequately and inadequate diameters of the maternal bony pelvis. Contractures of the maternal pelvis may occur in one or more diameters of the pelvic inlet, midpelvis, or pelvic outlet. Fetal macrosomia (fetal weight > 4,000 g), incomplete flexion of the fetal head onto the chest, occiput-posterior or transverse fetal position, and inability of the fetal head to mold to the maternal pelvis all contribute to the syndrome. Studies show that women with body mass indices in the obese range are more predisposed to cesarean deliveries related to dystocia and large-for-gestational age fetuses, which is consistent with FPD.
Dystocia is considered a complex disorder with significant genetic and environmental components. Predictors for FPD, such as maternal height and shoe size, are quantitative genetic traits. Other risk factors with genetic contributions include paternal height and large head-to-height ratios in both parents.
Gender, ethnic/racial, and life span considerations
Any woman of childbearing age may experience FPD, although women who have already delivered one or more infants vaginally have less risk of FPD than those having their first vaginal delivery. Teenagers under the age of 18 have an increased risk of FPD because their pelvic growth may not be fully completed. Ethnicity and race have no known effects on the risk for FPD.
Global health considerations
The World Health Organization (WHO) recommends that the optimal cesarean section rate is 15% of deliveries. Those countries with cesarean rates under 10% are considered to be underusing the technique. The U.S. national cesarean section rate is over 30%, which is considered by the WHO as overuse of the technique. There has been a striking increase in cesarean sections in medium- and high-income countries around the world, which most experts agree increases complications for both mothers and babies.
Patients may have a family history of fetal macrosomia or pelvic contractures. Any personal history of rickets, scoliosis, or pelvic fracture should also be noted. Gestational diabetes, which may contribute to fetal macrosomia, may be present. Ask the patient about her prior deliveries to ascertain whether she has delivered an infant vaginally before.
Determine the pelvic type of the woman. Android and platypelloid pelvic classifications are not favorable for a vaginal birth; the gynecoid and anthropoid pelvis classifications are present in 75% of all women and are favorable for a vaginal birth. Perform an internal examination; the following findings indicate a contracted pelvis and a potential for FPD to occur if the woman becomes pregnant: ability to touch the sacral promontory with the index finger; significant convergence of the side walls; forward inclination of a straight sacrum; sharp ischial spines with a narrow interspinous diameter; and a narrow suprapubic arch.
Common assessment findings with FPD during labor include delayed engagement of the fetal head, a lack of progress in cervical effacement, and dilation in the presence of adequate uterine contractions. If FPD is suspected during labor, physical assessment should include pelvic size and shape; fetal presentation, position, attitude, and presence of molding or caput succedaneum of the fetal head (swelling on the presenting part of the fetal head during labor); fetal activity level; maternal bladder distention and presence of stool in rectum; duration, frequency, and strength of contractions; effacement and dilation of the cervix; and descent of the fetal head in relation to the mother’s ischial spines. If fetal hypoxia or hypoglycemia occurs, loss of fetal heart rate variability, late decelerations, or fetal bradycardia may be seen on the electronic fetal monitor. Fetal scalp stimulation may fail to elicit heart rate acceleration, and fetal capillary blood pH obtained by scalp sampling may indicate acidosis.
Assess the patient and partner (or other labor support people present) for the ability to cope with the difficult labor and ability to maintain a positive self-concept and role performance. Assess the presence of anxiety or fear related to the mother’s or baby’s well-being or to medical interventions, such as forceps or vacuum extractor use or cesarean delivery. Feelings of exhaustion, disappointment, or failure are common.
General Comments: FPD cannot be diagnosed except in rare cases without allowing labor to proceed for several hours. In labor, the pubic symphysis and other pelvic joints gain mobility under the influence of high levels of relaxin and other hormones. Therefore, evidence of lack of progressive dilation and fetal descent in labor is usually considered more important than pelvic measurement in diagnosing FPD. During the second stage of labor, if there is progress in fetal descent, cesarean sections can be delayed up to 4 hours as long as long as there are no other fetal or maternal implications.
|Test||Normal Result||Abnormality With Condition||Explanation|
|Clinical pelvimetry||Diagonal conjugate > 11.5 cm; outlet > 8 cm||Diagonal conjugate < 11.5 cm; outlet < 8 cm||An adequate pelvic inlet and outlet is needed for a vaginal delivery|
Primary nursing diagnosis
DiagnosisRisk for injury of mother or fetus related to traumatic delivery
OutcomesRisk control; Risk detection
InterventionsLabor induction; Intrapartal care: High-risk delivery; Electronic fetal monitoring: Intrapartum; Intrapartal care
Planning and implementation
medical.Medical management of FPD can include the use of Pitocin to induce or augment labor contractions, manual or forceps rotation of the fetus into an occiput anterior position, and vaginal delivery assisted by outlet forceps or vacuum extractor. The cutting of a midline or mediolateral episiotomy is often necessary. If shoulder dystocia occurs, the McRoberts maneuver (extreme flexion of the mother’s legs at the hips) and firm suprapubic pressure may accomplish delivery. In some cases, intentional fracture of the infant’s clavicle is used to accomplish delivery in the presence of severe shoulder dystocia. When vaginal delivery appears to be impossible or likely to be very traumatic, cesarean delivery is indicated.
Labor patients using analgesia or anesthesia require careful monitoring. For patients using narcotic analgesics, monitor the maternal pulse, blood pressure, and respirations. Watch for signs of respiratory depression. Because intravenous (IV) narcotics readily cross the placenta, observe the fetal heart rate; often, a temporary loss of variability is seen. For patients using regional anesthesia, monitor maternal pulse, blood pressure, and respirations. Check the mother’s blood pressure every 1 to 5 minutes for 15 minutes after the epidural or spinal bolus dosage and then every 30 minutes. Watch for lowered blood pressure.
|Medication or Drug Class||Dosage||Description||Rationale|
|Opioid analgesics; anesthetics||Varies with drug, usually given IV push or via epidural||Pain relievers||Labor is difficult and prolonged; often back pain is increased owing to the position of the fetus; episiotomy repair and forceps or vacuum extraction require anesthesia|
|Oxytocin (Pitocin)||Mix 10 units in 500 mL of IV solution, begin infusion at 1 mU/min; increase 1–2 mU/min q 15–30 min until adequate labor is established||Oxytocic||Appropriate to induce labor or to give the patient a trial labor; should be discontinued upon a definitive diagnosis of FPD, requiring a cesarean section|
Have the laboring woman change positions frequently (approximately every half hour) to encourage movement of the fetal head into a favorable position for delivery. Sitting, squatting, positioning on hands and knees, or side lying (alternating sides) may be used. Avoid supine positioning. To encourage rotation of a fetus from a posterior position, suggest lying on the same side as the fetal limbs or position the mother on her hands and knees. Pelvic rocking exercises may be helpful. Encourage periods of ambulation as long as the membranes are not ruptured or the fetal head is well applied to the cervix.
Keeping the bladder and rectum empty allows maximum pelvic space for the descent of the fetal head. Fluid and caloric intake should be attended to during labor. In some delivery settings, however, patients may receive IV solutions for electrolyte, fluid, and/or glucose intake. In other settings, ice chips, clear liquids, or a light diet may be encouraged.
In the second stage of labor, instruct the laboring woman to use her diaphragm and abdominal muscles to bear down during contractions. Help her find a comfortable and effective position for pushing, such as supported squatting, semi-sitting, side lying, or sitting upright in bed or on a chair, birthing stool, or commode. Perineal massage during pushing will help decrease the likelihood of an episiotomy or decrease the degree of episiotomy needed.
Provide encouragement of the patient’s coping strategies and assistance with pain management. Nonpharmacologic aids that can be offered include breathing techniques, massage, sacral counterpressure, rocking chair, application of heat or cold, visualization or relaxation techniques, therapeutic touch, music, showering or bathing, companionship, and encouragement. Provide emotional support; families are often unprepared to deal with an unplanned, unwanted cesarean birth.
Evidence-Based Practice and Health Policy
Tsvieli, O., Sergienko, R., & Sheiner, E. (2012). Risk factors and perinatal outcome of pregnancies complicated with cephalopelvic disproportion: A population-based study. Archives of Gynecology and Obstetrics, 285(4), 931–936.
- In a retrospective population-based study including 242,520 women with singleton pregnancies, 673 women were diagnosed with cephalopelvic disproportion (CPD). Among women with CPD, nonreassuring fetal heart rate patterns were 3.5 times more likely to occur (95% CI, 2.8 to 4.3), and infants were 1.7 times more likely to have meconium-stained amniotic fluid (95% CI, 1.5 to 2.1) and 5.4 times more likely to have Agpar scores less than seven at 1 minute postdelivery (95% CI, 4.5 to 6.4) (p < 0.001).
- Women with CPD were also 4.6 times more likely to experience laceration of the cervix (95% CI, 2.3 to 9.2), 7.8 times more likely to experience uterine rupture (95% CI, 2.5 to 24.7), and 7.7 times more likely to succumb to intrapartum death (95% CI, 2.8 to 20.8) (p < 0.001).
- Compared to women without CPD, women diagnosed with CPD were also 2.9 times more likely be diagnosed with obesity (95% CI, 1.8 to 4.6; p < 0.001), 1.4 times more likely to be diagnosed with gestational diabetes mellitus (95% CI, 1 to 1.8; p = 0.028), and 2.2 times more likely to be diagnosed with polyhydramnios (95% CI, 1.6 to 2.9; p < 0.001) during pregnancy.
- Progress in labor: Cervical effacement and dilation, station of fetal head, presence of molding or caput, contraction pattern
- Factors contributing to FPD: Pelvic size and shape; fetal presentation, position, and attitude; maternal position; bladder and bowel fullness; duration, frequency, and strength of contractions
- Indicators of fetal well-being: Fetal baseline heart rate, variability, presence of accelerations and decelerations; fetal activity level; response to scalp stimulation
- Indicators of maternal well-being: Tolerability of labor pain, effectiveness of coping strategies, presence of support people, indicators of psychological status, vital signs