Dystocia- Causes, Risk Factors, and Management

What Is Dystocia?

The American College of Obstetricians and Gynecologists (ACOG) defines dystocia as abnormal or prolonged labor caused by abnormalities in-

1. The power (uterine contractions or maternal expulsive forces).

2. The passenger (position, size, or presentation of the fetus).

3. The passage (pelvis or soft tissues).

Dystocia, or abnormal labor progression, affects one-third of all cesarean sections and half of the primary cesarean sections in nulliparous women (first-time mothers).

What Are the Various Types of Dystocia?

The following types of dystocia are present-

• Cervical Dystocia- Cervical dystocia is a condition in which the cervix fails to dilate during labor. Previous cone biopsy or cauterization for cervical dysplasia can cause cervical dilatation to fail. Trauma is another reason for the inability of the cervix to dilate. When there are uncoordinated uterine contractions, cervical dilation failure might occur, which should respond to oxytocin. If the dystocia persists, the infant must be delivered via cesarean section.

• Shoulder Dystocia- The head of the infant normally lies to the left during the peripartum period, turns to the occipito-anterior position, and the head is delivered first. After that, the shoulders lay in an anteroposterior position before passing through the pelvic brim. The infant can inhale if the shoulders become trapped in this position since the mouth and nose are out of the vagina; however, the chest cannot expand because it is stuck in the pelvic brim. If the fetus is not delivered immediately, hypoxia will set in, and the fetus will die. The anterior shoulder usually impacts the maternal symphysis. The posterior shoulder has a less common impact on the sacral promontory.

What Are the Causes of Dystocia?

Dystocia can occur due to the following causes-

• Uterine Factors- Contractions must begin at the fundus and work their way down to the pelvis. Labor will be challenging and prolonged if the uterine activity is uncoordinated and contractions are short or infrequent. Primigravid mothers (women pregnant for the first time) are more likely to develop dystocia because they have a degree of uterine incoordination, which explains why their labors are longer. Uterine contractions can be aided and coordinated by oxytocin.

• Fetal Factors- The fetal factors responsible for dystocia include-

  • Fetal position or lie (transverse or breech position).

  • Macrosomia (fetal birth weight more than or equal to 4.5 kg).

  • Shoulder dystocia (this occurs as a combination of fetal factors and pelvic passage factors).

• Pelvic Passage Factors- A round brimmed pelvis is ideal for labor; nevertheless, some women's brims are lengthy and oval. If the fetal head has not engaged into the pelvis by 37 weeks of pregnancy in a primigravida, a tiny pelvic brim should be suspected. Scoliosis, kyphosis, and rickets are further causes of cephalopelvic disproportion. Shoulder dystocia is caused in part by a small or abnormal pelvic inlet.

What Are the Risk Factors for Dystocia?

The following factors increase the risk for dystocia-

• Maternal diabetes mellitus increases the risk of birth by two to four times compared to babies of the same weight born to moms who do not have diabetes.

• Prolonged labor, either in the first or second stage, or secondary arrest.

• Fetal macrosomia affects 48 % of babies that weigh under four kilograms.

• History of shoulder dystocia.

• Use of oxytocin (hormone used to induce labor).

• Labor induction.

• Obesity in mothers (BMI of more than 30 kg/m2).

• Forceps or ventouse are used to assist in vaginal birth.

How Is Dystocia Treated or Managed?

The dystocia is managed or treated according to the following factors-

• According to National Institute for Health and Care Excellence (NICE) guidance, pregnant women with diabetes who have a normally growing fetus should be offered elective birth by induction of labor or cesarean section, if needed, between 37 and 38 weeks of gestation.

• In women with pre-existing or gestational diabetes, the risks and benefits of elective cesarean, induction of labor, and vaginal birth should be addressed when the estimated fetal weight is greater than 4.5 kg.

• After past shoulder dystocia, either an elective cesarean or a vaginal delivery may be appropriate. The mother and her caregivers should make the decision together, considering the severity of any previous injuries, maternal preference, and expected fetal growth.

Management of Shoulder Dystocia:

The following steps are utilized for the management of shoulder dystocia during labor and delivery-

• Attendants should be on the watch for indicators of potential dystocia. They should keep a keen eye for difficulty in delivery of the fetal head, the head retained in place on the vulva, or a retracting head (turtle-neck sign), failure of the head to restitute, or failure of the shoulders to descend.

• The mother should stop pushing as this could aggravate shoulder impingement and raise the risk of a brachial plexus injury. It is best to avoid putting downward traction on the fetal head.

• McRoberts' Maneuver- The patient hyper flexes and abducts her hips so that they are against her abdomen. The lumbosacral angle is flattened, and the pelvis' anteroposterior diameter is increased. Mothers in labor may lack the energy to do this on their own and will require assistance. This is the most efficient and least invasive technique, so it should be done first. If this does not work, an episiotomy may be required to allow the obstetrician to try second-line maneuvers-

  • Rubin's maneuver (press on the fetal shoulder's posterior side to make more room for the anterior shoulder to be delivered).

  • Woods' screw maneuver (the anterior shoulder is rotated to the posterior position).

  • Posterior shoulder delivery.

• However, the need for a cesarean section should be considered at all times and should not be postponed.

What Complications Can Arise Due to Dystocia?

• Maternal Complications-

  • Postpartum hemorrhage.

  • Bladder rupture.

  • Third-degree and fourth-degree perineal tears occur in 3.8 % of dystocia deliveries.

  • Sacroiliac joint dislocation.

  • Vaginal lacerations.

  • Cervical tear.

  • Uterine rupture.

  • Lateral femoral nerve neuropathy.

  • Symphyseal separation.

• Fetal Complications-

  • Brachial plexus injury.

  • Fractured humerus or fractured clavicle.

  • Perinatal morbidity and mortality from hypoxia and acidosis.

  • Pneumothorax.

Conclusion:

Labor dystocia refers to labor that is unusually slow or lengthy. It can be detected initially (from the start of contractions to complete cervical dilatation) or during the second stages of labor (complete cervical dilation until delivery). Prolonged labor can raise the risk of infection in both the mother and the baby, fetal distress, newborn hypoxia, uterine rupture, and postpartum hemorrhage. It can also indicate a higher risk of pelvic floor and genital injuries during delivery (with subsequent increased risk for future incontinence and pelvic organ prolapse). Therefore, the fundamental justification for performing a cesarean delivery for the primary indication of labor dystocia is to reduce the chance of these negative mother and newborn outcomes.