The incidence of shoulder dystocia is generally reported as less than 1 percent. According to Varney’s Midwifery, shoulder dystocia may occur from 0.2 to 2 percent of vaginal cephalic deliveries, yet an accurate figure probably does not exist due problems with accurately establishing the incidence of shoulder dystocia. The textbook also notes that defining shoulder dystocia is critical to determining what steps to take to resolve it. The basic and anatomically correct definition of shoulder dystocia refers to cephalic presentations in which the anterior shoulder is wedged above the symphysis pubis instead of entering the true pelvis; however, in the clinical setting, the diagnosis is subjective and based retrospectively on observation. (Varney, p. 883)
Varney’s Midwifery cites two closely related types of dystocia that a midwife must be able to accurately diagnose as separate from actual shoulder dystocia— bed dystocia and snug shoulders.
Bed dystocia occurs when the woman is in a semi-Fowler’s or similar propped-up position and the baby is being born downward into the bed. Bed dystocia is especially common with a soft bed that sags under the woman’s buttocks. In such a situation, there is no room for delivery of the shoulders. This, however, is not shoulder dystocia. The problem is readily rectified by slipping something under the woman’s hips that elevates them and by reducing the upright angle of her position in the bed; or by bringing the buttocks to the edge of the bed; or by turning her on her side into the hand-knees position. It is an error to record such an event as an incidence of shoulder dystocia. (Varney, p. 884)
Often mistaken for shoulder dystocia are snug shoulders.
Snug shoulders are often given the misnomer “mild” shoulder dystocia and most likely do not meet the definition of the impingement (or impaction) of the anterior shoulder or both shoulders above the pelvic brim. Snug shoulders can occur with a large baby, an adequately shaped pelvis, and a somewhat obese mother, which together comprise a soft tissue dystocia. The head is born very slowly but the midwife does not need to push the perineum back manually in order for the head to be born. The baby’s face is fat but the baby does not really exhibit the turtle sign as the head goes through both resuscitation and external rotation. The shoulders are tight and take more effort to deliver, but making sure the shoulders are in the oblique diameter of the pelvis, a little suprapubic pressure, and an exaggerated lithotomy position readily take care of the problem, as does having the mother get into the hands-knees position. (Varney, p. 884)
The hands-knees position is widely known as the Gaskin Maneuver, named for midwife Ina May Gaskin. The following precautions can be taken to help reposition a woman in the event of a shoulder dystocia, according to the article “A New (Old) Maneuver for the Management of Shoulder Dystocia” on The Farm’s web site:
It takes surprisingly little time (as little as 30 seconds) to get a patient to her hands and knees, even in the event of an unexpected shoulder dystocia, such as the one reported here, and it can be accomplished even more quickly in a patient with more than one known risk factor if the following precautions are taken in advance:
1. Encourage the mother to assume the all-fours position at intervals during labor. It is a very comfortable position, especially when the baby is occiput posterior, and it is useful for facilitating rotation and descent. Admittedly, not all mothers will be comfortable in this position, or it may be one of many different positions assumed by the patient during the course of her labor, but it will help if she becomes familiar with this position in advance of the birth. Advise her that it may become necessary to assume this position again for delivery of the shoulders.
2. Avoid intravenous lines. A heparin lock can provide emergency venous access without the restrictions of dangling IV lines.
3. For the same reason, avoid continuous electronic fetal monitoring equipment, or remove the belts as the vertex is delivered. Belts and cables are also restrictive, and studies have shown that auscultation of the fetal heart tones every 5 minutes during the second stage of labor is sufficient.
4. Along the same lines, avoid stirrups and extensive sterile drapes, and for obvious reasons, avoid epidural anesthesia.
5. Have at least two assistants present at the birth. Labor coaches can be helpful in facilitating rapid changes in position if necessary.
6. Finally, deliver the baby in a bed, not on a narrow delivery table. Consider using the lateral decubitus position, or better yet, complete the entire delivery in the all-fours position in those patients at high risk for a shoulder dystocia (Table 1).
Admittedly, these recommendations run counter to the whole technological approach to childbirth that has been developed over the past 20 years, and they are not likely to be adopted in large traditional centers. Although anecdotal reports indicate the maneuver has been used successfully in high-tech settings, we expect it to prove most useful in the context of the low-intervention approach to obstetrics that is most familiar to family physicians.
Varney, H., Kriebs, J., Gegor, C., & Varney, H. (2004). Varney’s Midwifery. Boston: Jones and Bartlett Publishers.