Shoulder Dystocia - Oren Zarif

Symptoms of shoulder dystocia include a protracted second stage of labor (pushing phase) and a difficult time getting the baby to descend. The obstetrician may try several maneuvers to widen the pelvis or help the fetus move its shoulders.

Fetal factors can also contribute to dystocia such as breech presentation, mentum posterior face presentations and a flexed hindlimb (turtle sign). Maternal risk factors for labor dystocia include diabetes mellitus, maternal obesity and prolonged labor.

Causes

Shoulder dystocia occurs when a fetus's shoulders are blocking the completion of their full birth. This condition is an emergency situation and must be handled quickly to ensure the baby's oxygen supply. When shoulder dystocia is not treated correctly, the fetus can suffer serious complications such as hypoxia.

In this type of dystocia, the fetus's shoulders are prevented from exiting the pelvis during childbirth although the uterus contracts normally. This is one of the most common types of dystocia and can be caused by a variety of reasons.

This condition may be due to a physical obstruction in the birth canal such as an abnormally narrow or contracted cervical dilation or conditions that restrict the baby's entrance into the vaginal canal. It is also possible for this type of dystocia to be due to a malpresentation such as an abnormally positioned fetus or a breech presentation.

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A more serious cause of obstructed labour is when the fetus's head or neck becomes wedged between the mother's pubic bone and the bony prominences at the base of her spine, or in the pelvic bones themselves. In this case, a veterinary surgeon would need to manually remove the fetus and then place it into a normal position.

Maternal causes of dystocia are generally divided into two groups: primary and secondary. Primary uterine inertia is usually due to failure of the uterus to respond to fetal signals or a lack of a Ferguson reflex (the fetus's distension of the cervix stimulates a neuroendocrine response resulting in oxytocin). Secondary uterine inertia is often due to fatigue of the uterus myometrium caused by over-stretching during parturition or a combination of factors such as a large litter size, overly large fetuses, maternal obesity or systemic disease.

In both dogs and cats, a CBC and serum biochemical analysis should be performed (at least PCV, total solids, blood glucose and ionized calcium concentration) prior to beginning treatment for dystocia. Abdominal radiographs are also essential to assess pelvic dimensions, the number of fetuses and a maternal history of previous dystocia. Treatment of a dystocia should begin with a careful administration of calcium to increase the strength of uterine contractions. Careful monitoring of the fetal heart rate and progress of labor is crucial to avoid injury or death to the fetus.

Diagnosis

The initial evaluation of dystocia involves a complete physical examination, including palpation of the abdomen and vagina. The uterus should be palpated for degree of distension and presence of contractions (Ferguson reflex). Abdominal radiographs should be obtained to determine if a fetus is still in the pelvic canal or the sac. A CBC and serum biochemical analysis should be performed (at a minimum, PCV, total solids, blood glucose concentration and ionized calcium). A progesterone concentration may also be useful. The fetal heart rate is usually normal and should be evaluated for signs of distress.

Dystocia is a common indication for cesarean section in nulliparae. It is the most common cause of maternal mortality in this population, and a significant contributor to the overall caesarean section rate of veterinary medicine. Despite the prevalence of the condition, no specific physical or radiographic indicator has been developed to identify females with predisposing factors for dystocia that will require medical intervention or cesarean section during labor. As a result, there is considerable variation in rates of medical augmentation of labour and incidence of cesarean sections for this indication in clinical practice worldwide.

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Diagnosis of a dystocia is often delayed because of the difficulty in confirming whether or not parturition has begun and is progressing normally. This can result in a deterioration of the mammary condition, as well as a delay in the administration of drugs to stimulate uterine activity.

It is important to identify the type of dystocia as obstructive or non-obstructive. Obstructive dystocia, which can be difficult to diagnose, occurs when a fetus becomes stuck in the birth canal or uterus and is unable to exit despite uterine contractions. Obstructive labour may be due to a breech position, a fetus with an abnormal head presentation or any other physical obstruction that prevents the fetus from expulsion.

Non-obstructive dystocia is typically a result of uterine inertia. Symptoms include failure of the uterus to respond to fetal stimulation, and may be associated with excessive fluids or an oversized fetus. In this case, the uterus can be stimulated to induce contractions by administering oxytocin. If this is unsuccessful, a manual extraction procedure may be required.

Treatment

In chimpanzees and macaques the most common cause of dystocia is breech birth. This is most often fatal for the fetus, but can also be life-threatening to the mother. She may die from uterine atony, physical exhaustion and shock if her plight is not discovered early and corrective measures taken (e.g., manual or surgical delivery of dead fetus, hydration and antishock therapy). In small multitocus species like marmosets and tamarins functional dystocia is more common than in larger primates. This is often due to a blockage of the vaginal canal by a large head or forelimb and can usually be relieved by lubrication and traction. In some cases the head and one forelimb may be repositioned into shoulder flexion to clear the space for the kid's passage.

In some species the uterus becomes torsioned during labor, a condition known as cervical dystocia or uterine inertia. This can be very difficult to diagnose and treat, and in some cases may result in fetal or maternal deaths. It can be caused by a number of factors, including multiple gestation (twins or triplets), pregnancy to term in obese women, and gestational diabetes. It can also be caused by the use of certain drugs, including epidural analgesia and the insertion of intrauterine catheters.

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Observation of the signs of dystocia and recording the progress of labor are essential in all cases. The timing of onset of labor, the length of the active phase of labor, and the rate of cervical dilation are all variable in nonhuman primates, which make it challenging to determine when dystocia is present. This lack of a definitive indication for labor and the uncertainty about when it is appropriate to begin medical treatment opens the door to marked variation in cesarean delivery rates between hospitals, which is not entirely attributable to the evidence on comparative effectiveness.

The decision to have a cesarean section should be based on the risk of maternal and fetal death, as well as considerations of cost and availability of services. In the case of true fetal-maternal disproportion, cesarean delivery may be lifesaving for both mother and baby.

Prevention

Although many factors contribute to dystocia, it is most commonly a result of maternal/fetal disproportion. Pregnancy management to reduce fetal weight differences between dams and bulls can significantly lower the incidence of difficult births. The focus of prevention is primarily directed at first-calf heifers, as they are the most susceptible to dystocia. Genetic improvement using expected progeny differences (EPDs) has reduced the occurrence of dystocia in these animals, especially when calving ease is an EPD trait.

Maternal/fetal disproportion most often occurs as a result of the fetus being too large for the mare’s pelvic canal. This condition, known as shoulder dystocia, is a significant contributing factor to abortions and stillbirths. In some cases, it can also result in a calf becoming trapped between the mother’s legs. The presence of excessive uterine pressure and fundal pressure on the fetus’ shoulders may be exacerbated by a sudden increase in labor rates, pauses during dilation or failure to progress to stage 3.

Fetal malposition is another common cause of dystocia. This can include abnormal positioning of the fetus in the birth canal, such as head down, breech or transverse position. It can also include the fetus being flexed or extended above or below the pelvic ring. If lubrication and gentle traction fail to relieve these types of dystocia, they may be diagnosed as severe and will require medical or surgical intervention.

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Diagnosis of dystocia involves collection of a full reproductive history, a physical examination and laboratory tests to evaluate the mother and fetus. A radiograph of the cervix is often taken to assess cervical dilation. Occasionally, a Doppler ultrasound is used to evaluate fetal heart rate.

In the event of a suspected case of dystocia, the attending veterinarian should be promptly notified and he or she should immediately begin assessing the presenting situation. The veterinary technician should be prepared to assist with manual or surgical delivery of a dead calf, in the event that a veterinary physician is not available. The veterinary technician should also be prepared to provide the mother with fluid therapy and to give her antibiotics if necessary to prevent infection.

Shoulder Dystocia – Oren Zarif

Causes

Diagnosis

Treatment

Prevention

Weakness Symptoms - Oren Zarif

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