In a normal vaginal delivery, the baby’s head emerges first, followed shortly thereafter by the shoulders. In a small percentage of cases, one or both of the baby’s shoulders may become stuck under the mother’s pelvis bone. This can prevent delivery, and lead to a number of complications for both the mother and baby. When shoulder dystocia occurs, prompt intervention by the obstetric team may prevent serious birth injuries.
What Is Shoulder Dystocia?
Shoulder dystocia is a type of birth injury that occurs when the posterior shoulder, anterior shoulder, or both shoulders become trapped behind the mother’s pelvic bone during labour and delivery. Although this condition is relatively rare, it can cause serious problems for both the mother and baby. For babies with a birth weight of 2.5 kg to 4 kg, the incidence rate of shoulder dystocia is 0.6 to 1.4 percent. For babies weighing 4 to 4.5 kg, this rate rises to 5 to 9 percent.
This issue is often singled during the labour and delivery process by the “turtle sign,” where the fetal head emerges and then retracts back tightly against the mother’s perineum. Shoulder dystocia places both the mother and baby at a high risk of permanent birth-related injury. It is considered an emergency for the baby because of the potential for oxygen deprivation and other serious complications.
Potential Complications of Shoulder Dystocia
In some cases, both mother and baby recover fully from the problems caused by shoulder dystocia. However, there are cases where shoulder dystocia results in serious or even fatal birth injuries. According to the American College of Obstetricians and Gynecologists (ACOG), shoulder dystocia places both the mother and baby at risk of injury.
A baby may suffer from a number of complications, including:
- Clavicle or arm fractures
- Damage to the brachial plexus nerves; a brachial plexus injury can lead to a condition known as Erb’s palsy. A permanent brachial plexus injury may lead to paralysis of the affected arm.
- Lack of oxygen (asphyxia) from compression of the baby’s chest, which may cause brain damage or even death
- Prolapse or occlusion of the umbilical cord, which may lead to oxygen deprivation
- Hypoxic-ischemic encephalopathy (HIE)
Mothers may also suffer problems due to shoulder dystocia, such as:
- Postpartum hemorrhage (PPH), or heavy bleeding after giving birth
- Tearing of the perineum (the area between the vagina and rectum), which may require surgery to repair
- Uterine rupture, which may necessitate a hysterectomy to control the bleeding
Severe shoulder dystocia can lead to permanent disability for the baby and/or the mother.
Risk Factors for Shoulder Dystocia
Shoulder dystocia cannot always be predicted. In many cases, this issue does not become apparent until labour and delivery are already underway. However, there are certain risk factors that make shoulder dystocia more likely to occur.
Risk factors include:
- Fetal macrosomia: this condition is diagnosed when a baby weighs more than 4 kilograms at birth. Babies that are large for their gestational age (above the 90th percentile during pregnancy) may require intervention through a cesarean section (c-section) or other operative delivery.
- Diabetes: if the mother has diabetes, whether it is gestational diabetes or preexisting diabetes, it increases the likelihood of having a baby with high fetal weight. As such, the baby may be more likely to experience shoulder dystocia.
- Prior shoulder dystocia: if a mother previously gave birth to a baby who experienced shoulder dystocia, the risk of another baby having this birth injury is greater.
- Multiple pregnancy: a pregnancy involving twin, triplets or other multiples presents a greater risk for shoulder dystocia.
- Mother’s weight: if an expectant mother is overweight or gains too much weight during pregnancy, the risk of shoulder dystocia increases.
- Oxytocin Use: if doctors use oxytocin to induce labour, it may increase the likelihood of shoulder dystocia.
- Epidurals: when a mother receives pain medication through her lower back to numb her lower body during labour (an epidural), it may make shoulder dystocia more likely.
- Assisted vaginal birth: the use of tools such as a forceps or a vacuum to help the baby through the birth canal is the most common risk factor for shoulder dystocia.
- Length of second stage of labour: the second stage of labour is where the mother pushes to give birth. A very short or long second stage of labour increases the risk of shoulder dystocia.
- Past date of delivery: when the baby is past the expected date of delivery, it may suffer shoulder dystocia;
- Size of mother: a mother who is small or petite, or who has a narrow pelvis, has an increased risk of her baby suffering shoulder dystocia.
If one or more of these risk factors are present, an obstetrician-gynecologist may anticipate a difficult delivery and recommend an alternative, such as a c-section.
How Can Shoulder Dystocia Be Treated?
If an Obstet Gynecol physician anticipates a risk for shoulder dystocia, there are numerous steps that can be taken to ensure the safety of both the mother and baby. In some cases, a cesarean delivery may be necessary to reduce the possibility of shoulder dystocia.
In situations where a c-section is not scheduled, there are several steps that can be taken to attempt to move both the mother and baby into a better position. Proper management of shoulder dystocia may include:
- McRoberts Manoeuvre: flexing the mother’s legs, and bringing her thighs towards her abdomen
- Applying Suprapubic Pressure: pressing on the mother’s lower belly directly over her public bone in an attempt to push the baby’s shoulders clear of her pelvic bone
- Kristeller manoeuvre: applying fundal pressure to the uppermost part of the uterus towards the birth canal. There are contrasting viewpoints about the safety and efficacy of the Kristeller Manoeuvre, and studies have not yet been performed to determine whether fundal pressure is beneficial or may cause harm.
- Wood’s Corkscrew Manoeuvre: reaching inside of the mother’s vagina to manually rotate the baby’s posterior arm free
- Collarbone Fracture: breaking the baby’s collarbone to release their shoulders in more severe cases of shoulder dystocia
- Episiotomy: performing a surgical cut at the opening of the vagina during childbirth
By monitoring an expectant mother during pregnancy and throughout the birthing process, an obstetrical team can reduce the likelihood of serious complications from shoulder dystocia.