What Is Shoulder Dystocia?

Introduction

The birth of a child is a beautiful, natural process. Nonetheless, the process of labour and delivery of a child can sometimes take an unexpected turn and become stressful, or even dangerous, for both the mother and the baby. Unfortunately, one obstetric emergency that may arise during this process is shoulder dystocia, a condition in which the infant's shoulder gets stuck behind the mother's pubic bone during vaginal delivery. While it is a rare occurrence, shoulder dystocia must be quickly recognised and managed to avoid harm. If you are pregnant or planning to have a child, having an understanding of this condition can help you know what to watch for and promptly get the care you need. 

This article covers the basics of shoulder dystocia, including the causes, symptoms, treatment, and outlook for shoulder dystocia.

Definition of shoulder dystocia

Explanation of medical terminology

The medical term known as “dystocia” refers to any difficulty during childbirth. “Shoulder dystocia”, therefore, describes a difficult delivery specifically involving the baby's shoulders.

Occurrence during childbirth

Shoulder dystocia occurs during vaginal delivery when the baby's head passes out of the vagina completely, but one or both of the shoulders get stuck behind the mother's pubic bone. This prevents the shoulders from passing through the birth canal, delaying and complicating the delivery process.

Shoulder dystocia has historically been one of the most frightening and anxiety-inducing complications that can occur during labour and childbirth,¹ however with swift intervention, it can be adequately managed with minimal to no complications for both mother and child.

Incidence of shoulder dystocia

Shoulder dystocia is considered a relatively rare obstetric complication; estimates of how frequently it occurs can at times be inconsistent, but most sources report that it occurs in 0.15% to 2% of vaginal deliveries.²  

Causes and risk factors

Certain risk factors make shoulder dystocia more likely, particularly foetal macrosomia and maternal diabetes. ³ Still, shoulder dystocia can occur even in the absence of known risk factors. ⁴

Foetal factors

1. Macrosomia - having a baby that is larger than the average size, medically defined as “macrosomia”, increases the risk of the baby being stuck in the birth canal. Estimated foetal weights over 8 lbs 13 oz (approximately 4kg) are considered “macrosomic” and raise concerns of shoulder dystocia. 
2. Abnormal foetal position - when the foetus takes up an awkward position in the womb, such as a face-first rather than crown-first presentation otherwise known as foetal malpresentation), it may contribute to shoulder dystocia.⁵ 

Maternal factors

1. Gestational diabetes - mothers with gestational diabetes, or pre-existing diabetes, often give birth to larger infants ⁶ 
2. Pelvic anatomy issues - mothers with a naturally narrower pelvis may be more prone to having the complication of shoulder dystocia as the small pelvic size reduces the space for the baby to pass through. Medically, this condition is referred to as cephalopelvic disproportion.

Other contributing factors

1. Prolonged labour - if the process of labour is long and difficult, the baby can become distressed, increasing the likelihood of shoulder dystocia²  
2. Induction and augmentation of labour - medically induced or sped-up labour may cause the process to become somewhat uncoordinated, possibly leading to foetal malposition, subsequently resulting in shoulder dystocia.

Signs and symptoms

Clinical presentation during labour

1. Delay in delivery of the infant's shoulders - when a failure of the shoulders to descend beyond the vaginal canal is noticed despite active maternal pushing, this is the hallmark sign of shoulder dystocia.² 
2. Foetal distress indicators - when the occurrence of dystocia is prolonged, it severely stresses the foetus, which is observable on foetal heart rate monitors. Medically, this is known as foetal distress.

Diagnosing shoulder dystocia

Intrapartum assessment

Usually, a simple clinical observation of delayed shoulder delivery following the emergence of the baby’s head is sufficient to diagnose shoulder dystocia.²

Use of medical imaging techniques

Imaging techniques, in this case, are used preemptively: if the risk factors, such as a past medical history of diabetes or shoulder dystocia in a previous pregnancy, are present and noted during early pregnancy, imaging techniques such as ultrasounds are available to predict possible shoulder dystocia.⁴ 

Complications

Maternal complications

1. Vaginal tears - after the head of the baby is delivered, gentle downward traction is used to deliver the shoulders of the baby. If shoulder dystocia occurs at this point, and an excessive amount of downward traction is applied to free the infant, it may cause vaginal or perineal tears.  
2. Postpartum haemorrhage - prolonged labour due to shoulder dystocia may lead to a condition called uterine atony or may lead to lacerations within the birth canal, which can cause excessive bleeding after delivery.

 Foetal complications

1. Brachial plexus injuries - a particularly important group of nerves known as the brachial plexus is located around the neck and shoulders. This group of nerves is prone to sustaining damage in the event of shoulder dystocia, causing temporary or permanent paralysis of the arm.⁷
2. Hypoxic-ischemic encephalopathy - Hypoxic-ischaemic encephalopathy describes a lack of oxygen to the brain around the time of birth. This may result in neurological impairment, which is often irreversible.⁷

Management and interventions

Intrapartum management

1. Standard manoeuvres to resolve shoulder dystocia - specific rotations of the baby’s body, such as the McRoberts manoeuvre and suprapubic pressure (applying pressure on the lower abdomen just above the pubic bone)  may be systematically attempted to resolve shoulder dystocia.⁷ 
2. Involvement of obstetric and neonatal teams - at this stage of childbirth, if dystocia is encountered, part of the management of the condition is to involve additional personnel to carry out manoeuvres and monitor the mother and baby adequately.

 Medical interventions

1. Episiotomy - An episiotomy is a deliberate and controlled cut made to the perineum, which enlarges the vaginal opening to accommodate the delivery of the shoulders.
2. Emergency caesarean section - if all attempted manoeuvres fail, a caesarean section, also known as a C-section, may urgently be performed to deliver the baby.

Prevention strategies

Antenatal care and screening

1. Monitoring foetal size - Third-trimester ultrasound scans may help to estimate the size of the baby and the risk of shoulder dystocia.⁴ 
2. Identifying other aforementioned risk factors throughout the pregnancy  

Intrapartum care

1. Monitoring labour progress - a good birthing facility will pay close attention to slow progress of labour or failure of the foetus to descend adequately through the birth canal, and would communicate and address potential problems swiftly and effectively.
2. Decision-making for mode of delivery - for very large babies or diabetic mothers, planned C-sections may be recommended.  

Prognosis and follow-up

Short-term effects on mother and infant

1. Immediate health concerns - In the aftermath of delivery, the mother should be monitored for bleeding and tears, while the baby should be checked for any signs of oxygen deprivation. ⁸ 
2. Postpartum recovery - it is important to pay attention to both physical and emotional well-being. after experiencing dystocia of any kind, including shoulder dystocia, as recovery may be complicated following a traumatic birth.

 Long-term effects

1. Neurological outcomes for the infant - permanent injury to the brachial plexus and delayed achievement of the basic developmental milestones may occur.  ⁸
2. Psychological impact on the mother - birth complications can have long-term implications on maternal mental health. Conditions such as postpartum depression or PTSD (post-traumatic stress disorder) may arise after a stressful dystocia delivery.⁹

Summary

In conclusion, shoulder dystocia is an emergency situation in which the baby’s shoulder is trapped in the birth canal during the process of vaginal delivery. Quick recognition and coordinated management are crucial to prevent harm and avoid dire future consequences. 

Now that you know the basics of shoulder dystocia, you should also consider the importance of working closely with your care team before and during birth for prevention, early detection, and optimal management if complications like dystocia arise.