How Likely is Shoulder Dystocia? Factors and Evidence

Shoulder dystocia is a rare but potentially serious complication that can occur during childbirth, and it understandably raises concerns for expectant parents. Although the chance of it happening may seem frightening, it’s important to have accurate information on how likely shoulder dystocia is, and what measures can be taken to reduce the risk. In this article, we will explore the likelihood of shoulder dystocia during pregnancy, provide insights into its causes, and discuss the role of antenatal care in managing and mitigating this risk.

What is Shoulder Dystocia?

Shoulder dystocia is a situation during delivery when one or both of the baby’s shoulders become stuck behind the mother’s pubic bone, preventing the baby from being born in the normal manner. It occurs when the baby’s shoulders are too large to fit through the pelvic opening or when they are positioned in a way that makes it difficult for the baby to pass through the birth canal. Although it can happen during a vaginal birth, shoulder dystocia is more common in certain circumstances, and it can lead to complications for both the baby and the mother.

How Likely Is Shoulder Dystocia?

The occurrence of shoulder dystocia is estimated to be between 0.2% and 3% of vaginal births, depending on factors like maternal health, fetal weight, and the type of delivery. While this may seem like a small percentage, the fact that it can have serious consequences for both mother and baby makes it an important issue to consider during pregnancy. According to a study published in the British Journal of Obstetrics and Gynaecology, shoulder dystocia occurs in approximately 1 in 1,000 vaginal deliveries in the UK. However, the rate may be higher in cases where risk factors are present. Although these statistics show that shoulder dystocia is a relatively uncommon occurrence, understanding the risk factors can help guide prenatal care and delivery plans.

Risk Factors for Shoulder Dystocia

There are several antenatal risk factors that can increase the likelihood of shoulder dystocia, although it is important to remember that even without these risk factors, shoulder dystocia can still occur. Some of the main risk factors include:

1. Maternal Obesity

Women with higher BMI (Body Mass Index) are at an increased risk of shoulder dystocia, as obesity can lead to complications such as gestational diabetes, which in turn may result in larger babies.

2. Gestational Diabetes

Gestational diabetes, which causes elevated blood sugar levels during pregnancy, can lead to a condition called macrosomia, where the baby becomes larger than average. Large babies are more likely to experience shoulder dystocia during delivery.

3. Previous Shoulder Dystocia

If a woman has experienced shoulder dystocia during a previous birth, the likelihood of it occurring in subsequent pregnancies increases. This is why antenatal care plays such an important role in identifying and managing this risk.

4. Excessive Weight Gain During Pregnancy

Excessive weight gain during pregnancy can contribute to the development of gestational diabetes and macrosomia, both of which increase the risk of shoulder dystocia.

5. Advanced Maternal Age

Women who are 35 years old or older may be at a slightly higher risk for shoulder dystocia, partly due to changes in the way the body responds to pregnancy and delivery.

6. Induced Labour or Prolonged Labour

When labour is induced, or if the labour is particularly long, there can be a greater chance of complications, including shoulder dystocia. Prolonged labour may lead to positional difficulties that can affect the birth.

How Can Antenatal Care Help Reduce the Risk?

While there are no guarantees that shoulder dystocia will be prevented, proper antenatal care can help reduce the risk of complications by managing the known risk factors. Here are some ways antenatal appointments and interventions can help mitigate the chances of shoulder dystocia:

1. Monitoring Fetal Growth

During your antenatal appointments, your doctor or midwife will monitor the growth of your baby. Regular antenatal scans can help identify if your baby is larger than expected (a condition known as macrosomia). If this is the case, your healthcare team may recommend adjustments to your delivery plan, such as considering a caesarean section to avoid complications during a vaginal birth.

2. Gestational Diabetes Screening

Gestational diabetes is a risk factor for shoulder dystocia, but it is also manageable if detected early. Antenatal care includes screening for gestational diabetes, which typically takes place around 24 to 28 weeks of pregnancy. If diagnosed, appropriate dietary changes, exercise, and in some cases, medication can help manage blood sugar levels and reduce the likelihood of having a large baby.

3. Weight Management and Nutritional Support

Your healthcare provider will provide guidance on managing weight gain during pregnancy, which can help reduce the risk of gestational diabetes and excessive fetal growth. Antenatal support often includes advice on maintaining a balanced, healthy diet and safe exercise options to promote both maternal and fetal health.

4. Pre-Labour Discussions

If you have any risk factors for shoulder dystocia, your antenatal care provider will discuss a tailored birth plan with you. This can involve planning for a hospital birth where medical professionals are prepared to handle complications, such as shoulder dystocia, should they arise.

5. Antenatal Education and Classes

Attending antenatal education classes can provide you with information on how to manage your pregnancy, the delivery process, and what to expect during childbirth. Many classes also discuss potential complications, including shoulder dystocia, helping you feel more prepared and informed about your options.

How is Shoulder Dystocia Managed?

If shoulder dystocia occurs during childbirth, it is a medical emergency, and healthcare providers are trained to manage it quickly and safely. The following steps are commonly used to resolve shoulder dystocia:

• McRoberts Maneuver: This involves the mother being positioned with her legs raised and pulled back towards her chest, which can help release the stuck shoulder.
• Suprapubic Pressure: Applying pressure just above the pubic bone can help dislodge the baby’s shoulder.
• Delivery of the Posterior Arm: Sometimes, the posterior (back) arm of the baby may be delivered to provide more room for the baby’s shoulders to pass through.
• Emergency Caesarean Section: In some cases, a caesarean section may be required if other measures fail. While shoulder dystocia is a rare complication, it is still important for expectant parents to be aware of the risk factors and the steps that can be taken to reduce the likelihood of its occurrence. With proper antenatal care, monitoring, and support, the risks associated with shoulder dystocia can be managed effectively, providing peace of mind for both the mother and the baby. By attending antenatal appointments regularly, engaging in antenatal fitness such as prenatal yoga, and working closely with your healthcare team, you can help ensure the safest possible birth experience. If you have concerns about your specific risks for shoulder dystocia, discussing these with your midwife or doctor will allow them to personalise your care and make informed decisions about your birth plan.