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Shoulder Dystocia
Sponsored by The Indian Health Service Clinical Support Center
4. Can Shoulder Dystocia be Prevented?
Case Scenario
Mrs. O is a 29 y/o G3P2 at 38 weeks gestation by an early ultrasound who has a BMI of 38.2 kg/M2. She has been diagnosed with gestational diabetes at 24 weeks and has had somewhat suboptimal glucose control throughout the pregnancy. An ultrasound obtained last week estimated the fetal weight as 4379 grams. She feels this baby is larger than her other infant who all weighed between 8-9 pounds and were delivered vaginally. Your clinical exam estimates the fetal weight at over 9 pounds. Pelvic exam reveals her cervix to be 2 cm dilated, 50% effaced, with a vertex presentation at -2 station. She inquires about whether she can deliver this baby normally. How would you counsel her? See Clinical Pearl on the ‘C C C Deliver Through’ maneuver below.
Because of the serious consequences of shoulder dystocia, various preventive strategies (Sanchez-Ramos) have been proposed. It would seem intuitive that if you suspect a woman may have a macrosomic (>4000 g) infant, you should get her delivered before it grows larger over time. Unfortunately the Cochrane database does not support this concept.
First, estimation of fetal weight is usually of suboptimal accuracy. Sonographic fetal weight estimations, especially at term, and in suspected large for gestational age infants, have at least a 20 per cent margin of error. So if the fetus is reported as having a weight of 4000 g, it could weigh 3200 g, or it could weigh 4800 g! If you have tried to do biometry on these fetuses you are aware of the errors incurred by not being able to get the whole abdomen or head onto the screen!
Clinical estimation of fetal weight has a similarly poor accuracy, even among experienced clinicians. Combining both estimates may give you a better “gestalt” about the fetal weight, as may the multiparous mother’s opinion about relative size of the current fetus compared to her prior children’s birth weights. Don’t be surprised however if the infant’s actual weight at birth isn’t what everyone expected! Several formulas for estimating relative head to abdomen, or head to thorax, ratios have been proposed, but all have relatively poor predictive values. Various scoring systems for predicting shoulder dystocia have likewise shown disappointing results.
Induction of labor for the indication of suspected fetal macrosomia has not been shown to prevent shoulder dystocia, brachial plexus injury, or lower rates of cesarean delivery when compared to expectant management. Labor induced for a diagnosis of macrosomia actually results in a higher cesarean birth rate. Elective cesarean delivery for suspected macrosomia results in a disproportionate increase in the cesarean rate compared with the reduction in the rate of shoulder dystocia.
Rouse et al reported on a decision analytic model was constructed to compare 3 policies: (1) management without ultrasound; (2) ultrasound and elective cesarean delivery for estimated fetal weight of 4000 g or more (4000-g policy); and (3) ultrasound and elective cesarean delivery for estimated fetal weight of 4500 g or more (4500-g policy).
Rouse et al found that for each permanent brachial plexus injury prevented by a 4500-g cesarean cut-off policy, 3695 cesarean deliveries were performed at an additional cost of $8.7 million, vs 2345 cesarean deliveries and $4.9 million with the 4000-g policy. In the baseline analysis for diabetic women, with all 3 policies, rates of cesarean delivery, shoulder dystocia and brachial plexus injury, and total costs were higher than for nondiabetic women. However, more favorable ratios for both cesarean deliveries and cost per permanent injury avoided were observed: 443 deliveries and $930 000, respectively, with the 4500-g policy, and 489 deliveries and $880 000, respectively, with the 4000-g policy. Sensitivity analysis confirmed the general robustness of these findings.
Therefore the Rouse et al decision analysis estimated that an additional 2,345 cesareans would be required to prevent one permanent brachial plexus injury from shoulder dystocia if fetuses suspected of weighing more than 4000 g underwent cesarean delivery. If only infants estimated to weigh more than 4500 g were subjected to cesarean, over half of the shoulder dystocias would be missed, and 978 cesareans would need to be performed to prevent one permanent brachial plexus injury.
Nevertheless, the analysis did suggest that in diabetic women with an estimated fetal weight of greater than 4500 g, prophylactic cesarean might result in benefit. It is important to consider the woman’s perspective as well. If a prior vaginal birth has resulted in significant fetal injury and perhaps severe perineal trauma as well, consideration of the mother’s preference for prophylactic cesarean would certainly seem to be reasonable.
Clinical Pearl: The ‘CCC Deliver Through’ maneuver for Shoulder Dystocia Prevention
If shoulder dystocia is a concern, some clinicians have empirically advocated immediately proceeding to delivery of the fetal shoulders to maintain the forward momentum of the fetus. (See ‘CCC Deliver Through’ maneuver for Shoulder Dystocia Prevention below) Others support a short delay in delivery of the shoulders, arguing that the endogenous rotational mechanics of the second stage may spontaneously alleviate the obstruction.
One maneuver to completely avoid shoulder dsystocia is to continue the expulsive momentum and deliver the presenting part on through to the visualization of the anterior shoulder without stopping for suctioning the oropharynx, fetal mouth, or nares, and/or to reduce a nuchal cord.
What does the ‘CCC Deliver Through’ maneuver entail?
If you have any suspicion that the patient may be at risk for shoulder dystocia, then consider the following:
Pre-‘CCC Deliver Through’ maneuver
First, try to gauge the expulsion of the head for the initial peak of a contraction, e.g., not at the end of third Valsalva maneuver in a 60-90 second contraction in an exhausted parturient.
If a regional anesthetic has been utilized, then also make sure that the anesthetic is at a nadir on motor function.
And now ‘CCC Deliver Through’ maneuver As soon as the head presents itself in the cardinal movements from extension, restitution and onto external rotation, the provider should continue that momentum with gentle posterior traction toward the rectum on the fetal parietal bones until you clearly see delivery of the fetal anterior shoulder emerging from beneath the symphysis. Alternately one hand can be over the face and the other hand on the occiput to continue the momentum.
At this time ask the mother to pant while you suction the infant as needed, or reduce any obstructing elements of the umbilical cord. Then ask the patient to continue to bear down gently and deliver the posterior shoulder and body.
Please note: This is unlike what some classic obstetrics texts recommend for the normal course of delivery of the fetal head. The main difference is that you do not halt the momentum after restitution or external rotation to suction the oropharynx. Also you do not halt the momentum to reduce a nuchal cord unless it is critically tight. Both suctioning and movement of the cord can be completed after delivery of the anterior shoulder.
After delivery of the anterior shoulder, then continue as you would normally, e.g., ask the mother to pant while you suction the oropharynx or manipulate the cord, then direct the fetal body anteriorly until the posterior shoulder passes the perineum to accomplish complete delivery. Please protect the perineum as you complete the delivery process after delivery of the anterior shoulder.
Pelvic Geometry
Once the head is out of the vagina, the head restitutes and the neck untwists. After a few moments, external rotation takes place as the shoulders move from the oblique to the anteroposterior diameter of the pelvis. One possible advantage is if the ‘CCC Deliver Though’ maneuver is done quickly enough, the accoucheur may deliver the anterior shoulder before the shoulders reach the full anteroposterior diameter of the pelvis that they achieve when external rotation occurs.
Caveat
While this maneuver seems to work 100% of the time in our less than random sample, we should be skeptical of anything that seems to work so well.
A random sample of ~10 providers on L/D had heard of it, and many did it when the suspected a risk of shoulder dystocia was an imminent risk. In fact it was so common that no one had a separate name for it….it was an unnamed automatic reflex. In addition, it seems to be used more commonly as the incidence of heavy parturients increases.
Would the ‘CCC Deliver Through’ maneuver increase perineal trauma? Or….?the old way has got to be the best way for the perineum. My experience with many, many deliveries the old way includes a few hundred 2nd degree lacerations (?10%) with the rare 3-4th degree laceration during delivery of the head or the posterior shoulder Yet, lacerations occurring during the delivery of the anterior shoulder, per se would be very rare….. for a ratio of ~ 0-1 / 1000+.
As the ‘CCC Deliver Through’ maneuver simply suggests that once the head is delivered….just do not stop to suction the oropharynx, or reduce the cord till you have the anterior shoulder out, and then do everything else the same…. the impact on perineal lacerations is probably closer to nil.
A better argument against this maneuver is that its effect is it is unstudied, e.g., perhaps just by the fact that one could perform the ‘CCC Deliver Through’ maneuver at all meant that the shoulder dystocia was not going to occur anyway….or that the development of the true shoulder dystocia geometry would not allow one to deliver through to the anterior shoulder regardless.
On the other hand, it may be more like the insurance business….if you have an expensive flood policy….then you’ll never even see a heavy drizzle.
