What is the management for a 33-year-old woman, gravida 2 para 1, at 40 weeks gestation with a history of previous cesarean delivery (C-section) due to breech presentation, now presenting with spontaneous rupture of membranes, normal blood pressure, and Category I fetal monitoring, who has dilated to 10 cm with fetal vertex at 0 station, occiput transverse, and shows signs of molding and caput on the fetal head after 4 hours?

From the Guidelines

This patient is experiencing arrest of descent during the second stage of labor, likely due to cephalopelvic disproportion, and the recommended management is to proceed with a cesarean delivery. Despite adequate uterine contractions (>200 Montevideo units), appropriate maternal pushing efforts, and reassuring fetal status (category I monitoring), there has been no descent of the fetal head after 4 hours in the second stage of labor. The presence of molding and caput formation on the fetal head indicates significant pressure against the maternal pelvis without progress. This patient has risk factors for cephalopelvic disproportion, including a previous cesarean delivery for breech presentation, which may indicate an underlying pelvic issue 1. While augmentation with oxytocin could be considered, the adequate contraction pattern (210 Montevideo units) suggests that inadequate uterine activity is not the issue. Attempting instrumental delivery would be inappropriate given the fetal station at 0 and occiput transverse position. Prolonging labor further increases risks of maternal exhaustion, chorioamnionitis, and potential fetal compromise. The cesarean delivery should be performed under the existing epidural anesthesia, with standard surgical preparation and antibiotic prophylaxis.

Some key points to consider in the management of this patient include:

• The importance of thorough cephalopelvimetry to exclude the presence of disproportion, as 40% to 50% of parturients with arrest of the active phase have concomitant cephalopelvic disproportion 1
• The potential risks of impacted fetal head at cesarean delivery, including maternal hemorrhage and injury to adjacent organs, as well as neonatal consequences such as skull fractures and brain hemorrhage 1
• The various techniques for managing impacted fetal head at cesarean delivery, including uterine relaxation, abdominal cephalic disimpaction, manual vaginal disimpaction, reverse breech extraction, and the Patwardhan method 1
• The potential complications of these techniques, including uterine incision extensions, need for blood transfusion, and infections, and the importance of efficient and skilled approach to reduce the duration of the impacted fetal head and the risk of direct trauma 1

Overall, the priority should be to prioritize the safety of both the mother and the fetus, and to proceed with a cesarean delivery in a timely and efficient manner.

From the Research

Fetal Head Molding

• Fetal head molding refers to changes in cranial bone relationships that occur in response to external compression force, allowing the fetal head to accommodate to the geometry of the passage 2.
• The process of fetal head molding involves the shortening of the suboccipito-bregmatic diameter and the lengthening of the mentovertical diameter, accomplished partially through the unbending or straightening of the parietal bones rather than the overlapping of sutures 2.
• Excessive fetal head molding can occur due to prolonged labor or strong contractions, leading to several disorders on the fetal head, and can be studied using finite element analysis of a fetal skull subjected to uterine pressures during the first stage of labor 3.

Factors Affecting Fetal Head Molding

• The effect of labor force on fetal head molding has been quantitatively investigated using a finite element modeling approach, showing that the fetal skull diameters and modified molding index (MMI) increase when the labor force is increased 4.
• The suboccipito-bregmatic diameter (SOBD) is more sensitive to the changes of labor force than other fetal skull diameters, and parietal bone around bregma and frontal bone around coronal suture undertake more stress and spatial and rotational displacement under larger labor force 4.
• Three-dimensional magnetic resonance imaging (MRI) and 3D finite element mesh reconstructions can be used to compare the fetal head between prelabor and the second stage of labor, demonstrating varying degrees of fetal head molding and brain shape changes 5.

Clinical Implications

• Fetal head molding can be observed using ultrasound and MRI, and can be affected by the presence of pelvic floor muscles, which can lead to a reduction in reaction forces and muscle stretching, indicating that sufficient molding may lead to fewer injuries 6.
• The relationship between labor force and fetal skull molding can be used to predict head injury by measuring the labor force during delivery, and excessive molding can result in cranial birth injuries and affect the infant shortly or even long after birth 3, 4.