How does forceps delivery cause cranial deformation, specifically ping-pong ball skull (cranial indentations)?

From the Guidelines

Forceps delivery can cause ping pong skull fracture by applying excessive pressure to the infant's head during birth, as the metal forceps compress the soft, malleable skull of the newborn, creating an indentation similar to how a ping pong ball can be dented. This occurs when the forceps blades make contact with the parietal or frontal bones of the infant's skull, pushing the bone inward without breaking into fragments, resulting in a depressed skull fracture or "ping pong" fracture 1. The newborn skull is designed to be flexible to allow passage through the birth canal, but this flexibility also makes it vulnerable to deformation when external pressure is applied.

Some key points to consider when evaluating the risk of ping pong skull fracture during forceps delivery include:

• The use of a single forceps as a lever to disimpact the head is considered dangerous and should be avoided 1
• The use of a vacuum at cesarean delivery has the potential to cause significant fetal injury, such as intracranial and subgaleal hemorrhage 1
• Alternative techniques for managing impacted fetal head at cesarean delivery, such as uterine relaxation, abdominal cephalic disimpaction, manual vaginal disimpaction, reverse breech extraction, and the Patwardhan method, may be considered to minimize the risk of fetal injury 1

While many ping pong fractures resolve spontaneously as the infant grows, deeper indentations may require medical intervention such as elevation of the fracture. The risk of this complication has led to more selective use of forceps in modern obstetric practice, with vacuum extraction often preferred as it generally causes less compression force on the infant's skull.

From the Research

Forceps Delivery and Ping Pong Skull Fractures

• Forceps delivery is a significant cause of ping pong skull fractures in newborns, as evident from studies 2, 3, 4, 5.
• The use of forceps during delivery can lead to mechanical traumatic factors, resulting in inward bowing of the skull bones, but its continuity remains intact 2.
• A cohort study found that out of 13 cases of depressed skull fractures, nine cases were associated with the use of instrumental delivery, with seven of those cases delivered vaginally using forceps 3.
• Another study compared "instrument-associated" and "spontaneous" obstetric depressed skull fractures and found that 50 depressed skull fractures were associated with instrument delivery, with all "instrument-associated" cases caused by forceps application or sequential instrument use 4.
• The correct use of forceps is crucial to avoid cranial lesions in newborns, especially in cases of difficult delivery 5.

Comparison with Other Delivery Methods

• A study compared the effects of vacuum extraction, forceps delivery, and cesarean section on mothers and fetuses, finding that forceps delivery increased the incidence of birth canal trauma and anemia 6.
• The same study found that vacuum extraction had a lower incidence of blood loss and febrile morbidity compared to cesarean section, and that infants delivered by vacuum extraction had a higher incidence of transient cosmetic deformations, whereas infants delivered by forceps had forceps marks and facial lacerations more frequently 6.

Incidence and Treatment

• The incidence of ping pong skull fractures is rare, with a study finding an incidence of 3.0 in 10,000 live births 3.
• Treatment for ping pong skull fractures is usually conservative, with spontaneous resolution, and the overall prognosis is excellent both neurologically and cosmetically 3, 4.
• However, some cases may require neurosurgical elevation of the depressed fracture, as seen in a case report where a ping-pong fracture was managed non-surgically with a vacuum extraction method 2.