There are several abnormalities at the time of labor initiation that can interfere with the orderly progression to spontaneous delivery.
These are generally known as dystocia.
Cervical dystocia is difficult labor caused by mechanical obstruction in the cervix.
Dystocia comes from the Greek “dys” which means “difficult, painful, messy, abnormal” + “tokos” which means “birth”.
Dystocia literally means difficult work and is characterized by abnormally slow work progress. The term dystocia describes the difficult delivery of a baby.
In dystocia the baby may present in the birth canal where the shoulder is trapped too long behind the pubic bone or at the opening of the birth canal.
Difficult delivery of the baby arises from distinct abnormalities that may exist individually or in combination.
Expulsive forces may be abnormal due to insufficiently strong uterine contractions, not being adequately coordinated to achieve dilation, or due to cervix-uterine dysfunction.
In addition, there may be inadequate voluntary muscle effort from the mother during labor .
Fetal abnormalities of presentation, position, or development can delay delivery.
Normal position for delivery
When the pregnancy is ending, the fetus is placed in a rearward-facing position, called the occiput anterior.
With the face and body to one side and the neck flexed, where the presentation to enter the birth canal is the head.
Pelvic fetus disproportion
Fetal pelvic disproportion is indicated when prenatal clinical estimates of the mother’s pelvic dimension, ultrasound findings, and labor becoming prolonged are made.
If increased labor restores normal progress and the weight of the fetus is less than 5 kg in women without diabetes or less than 4.5 kg in women with diabetes, labor can continue safely.
If progress is slower than expected in the second stage of labor, women are evaluated to determine if operative vaginal delivery (with forceps or vacuum extractor) is safe and appropriate.
The abnormal positions are oriented: forward called the posterior occiput and the face, forehead, buttocks and shoulders presentations.
Presentation of posterior occiput
A very common abnormal presentation of the baby for delivery is the occiput posterior.
The neck of the fetus is usually flexed, which will result in a diameter greater than that of the baby’s head that must pass through the birth canal in the pelvis.
Face or front presentation
In the face delivery presentation, the baby’s head is hyperextended, and this position is distinguished by the position of the chin.
When the chin is posterior, the head is less likely to turn and delivery is less likely to occur vaginally, thus requiring a cesarean section.
Breech presentation in front of the head is the second most common abnormal presentation.
Breech presentation is a problem primarily because the presenting part is a poorly dilating wedge, which can cause the ensuing head to become trapped during delivery, often compressing the umbilical cord.
When umbilical cord compression occurs, fetal hypoxemia can occur.
Factors that usually cause a baby to breech include:
- Preterm labor.
- Presentation of uterine abnormalities.
- Fetal abnormalities.
At the time of delivery, breech presentation may increase the risk of:
- That a trauma is caused at birth.
- If dystocia is present.
- Perinatal death occurs.
Complications are more effective and easier to prevent than to treat them, so whenever possible the baby’s presentation for delivery should be known in advance.
A cesarean section is usually performed at 39 weeks gestation or when the woman is in labor.
This technique consists of gently pressing the maternal abdomen to reposition the fetus.
This situation is infrequent, when the fetus presents, the shoulder lodges in the posterior part of the pubic symphysis after the fetal head appears, which prevents the delivery from being vaginal.
There are a variety of reasons why labor is difficult:
Delivery of large babies with unusually high body weight at birth. This can be caused by obese mothers, mothers, often small, who may have a small pelvic structure, or the presence of diabetes.
The mother’s pelvic dilation or opening does not reach an adequate size to allow the baby to pass normally. Possible causes include:
- Inadequate uterine activity.
- After surgical procedures.
This condition can be difficult to distinguish from lack of dilation due to uterine dysfunction, although uterine dysfunction must respond to oxytocin.
Cervical dystocia is treated by cesarean delivery.
Risk factors for abnormalities in labor include:
- A large fetus.
- Obese mother.
- Mellitus diabetes.
- Anterior shoulder dystocia.
- Operative vaginal delivery.
- Fast work.
- Prolonged work.
The risk of morbidity is the occurrence of a brachial plexus injury, bone fractures and increased neonatal mortality.
Signs and symptoms
Signs of shoulder dystocia are noticed when labor stops because the baby’s shoulders are lodged in the birth canal behind the pubic bone.
Signs also include very large babies who are likely to have trouble being born with a vaginal delivery.
Shoulder dystocia cannot be diagnosed until delivery.
But a prepartum ultrasound can reveal the baby’s size, if it is too large to pass safely through the birth canal.
Your doctor will decide the best treatment plan for you. Treatment options include:
- Manipulated vaginal delivery: There are a variety of maneuvers the doctor can do to help the mother deliver the baby.
- Cesarean delivery, if the maneuvers don’t work, the baby will need to be delivered via cesarean section.
It is not possible to prevent shoulder dystocia, babies at risk of shoulder dystocia due to their large size should be evaluated before delivery with ultrasound tests.
Women with diabetes, with pregnancies complicated by macrosomia, and at risk for shoulder dystocia should be counseled and delivered by caesarean section.
Delivery with shoulder dystocia
Once the obstetrician diagnoses shoulder dystocia, maneuvers that are performed sequentially are attempted.
The hyperflexed mother’s thighs are positioned to widen the pelvic outlet, this maneuver is known as the McRoberts maneuver and suprapubic pressure is applied to be able to rotate and dislodge the shoulder.
Fundus pressure is avoided because it can worsen the condition or lead to uterine rupture.
The doctor reaches into the posterior area of the vagina, pressing on the shoulder, and rotates the fetus to the most suitable position for safe delivery.
This maneuver is called the wood screw maneuver. The elbow is flexed and the baby’s arm and hand are passed across the chest to release the arm.
However, these types of maneuvers increase the risk of fractures of the humerus or clavicle.
When all these maneuvers are ineffective, the obstetrician reverses the labor movements, (Zavanelli maneuver), to deliver the baby by cesarean section.
Complications of dystocia
Complications of dystocia include:
For the baby
- Lack of oxygen.
- Broken arm or clavicle.
- Nerve damage
- Tear or bruising of the cervix, rectum, or vagina.
- Hematomas in the bladder.
- If fetal pelvic disproportion causes labor to progress more slowly than expected in the second stage of labor, women are evaluated to determine if operative vaginal delivery is safe and appropriate.
- In most cases, when the baby is presented with the posterior occiput, a cesarean section is necessary.
- In breech presentation, the presenting part is a poorly dilating wedge, which can cause the head to become entrapped during delivery, often compressing the umbilical cord.
- For breech presentation, a C-section is usually performed at 39 weeks or during delivery, but the external cephalic version is sometimes successful before delivery, usually at 37 or 38 weeks.
- When shoulder dystocia occurs, maneuvers are routinely performed to uncouple the shoulder. If these maneuvers are unsuccessful, the fetal head is repositioned into the vagina or uterus and a cesarean delivery is performed.