The best and worst brachial plexus injury literature

In Utero causation is a manufactured theory based on speculation that contradicts known anatomic and physiologic principles. For those who were attempting to remove excessive traction as the primary causative entity for birth injuries, expert articles began to focus on causation theories other than the obvious ones: provider panic and force. According to this effort, brachial plexus injury was touted to be a very-low-velocity and very-low-impact injury due solely to the inherent “forces of labor”. Supporters of this novel theory claim that it is possible to identify adverse combinations of factors, due to labor itself, which are associated with shoulder dystocia and neonatal injury.1

Since Sever, W. first proved that permanent brachial plexus palsy (BPP) cannot occur as a result of labor forces, many others have been intrigued by how commonly brachial plexus palsy occurs, how severely, and by what mechanism. Because stout traction applied during shoulder dystocia (SD) is a well-established mechanism of injury, traditionally, brachial plexus palsy noted at birth has been attributed to antecedent shoulder dystocia. Theories regarding brachial plexus injuries occurring without shoulder dystocia have been touted as failure to recognize the complication. Neonatal brachial plexus injury has many reported causes, though mechanisms unrelated to the birth process are extremely rare.2

In Utero Theory has been controversial since its relatively recent inception. According to Sever, if an in utero acquired Erb’s Palsy is relatively frequent, it should occur more often among neonates delivered by cesarean section, particularly since the rate of cesarean sections has been in the range of 25-35% for at least two decades. It was a matter of interest, since a published series of more than 200 brachial plexus injuries indicated that only one of the affected children was delivered by a repeat cesarean section. The delivery of this particular infant was complicated by macrosomia, two failed forceps attempts, and involved a Zavenelli maneuver (pushing the baby’s head back into the vagina/uterus after forceps dragged it out). There was serious doubt that, even in this single case, forces other than those used during delivery attempts were responsible for the baby’s injuries. Even a casual review of the literature proves that brachial plexus palsy follows shoulder dystocia. It appeared reasonable to Dr. Sever that if it occurs at all, brachial plexus injury unrelated to the process of delivery is a very rare phenomenon with little bearing on the overall problem of shoulder dystocia at birth.3

The research behind the In Utero Theory has been relatively easy to refute. RJ Jennett et al. first published an in utero causation article in 1992. It included two references that did not support their theory. 4 They assumed that if shoulder dystocia and strong traction were not recorded in the patient record, they did not happen. Jennett’s most recent article finally accepted that traction is a cause.5

More research on the absence of a recorded shoulder dystocia forced researchers to admit to “inherent ascertainment bias in his retrospective studies.6 Closer analysis of the data indicated that if you encounter a shoulder dystocia resulting in Erb’s Palsy, the likelihood that it would have occurred in the absence of shoulder dystocia was 0.19/18.25 = 1.04% . Hence, the likelihood that it is related to shoulder dystocia is 98.96%. (!) That the authors never performed this simple analysis of their data is telling in and of itself.

Spellacy WN et al. Reply: “Erb’s palsy without shoulder dystocia”. AJOG vol.179: No.2: August 1998 letters:

“Erb’s palsy without shoulder dystocia: To the Editors: In their recent article, Gherman et al. Found that 17 of 40 (42.5%) cases of Erb’s palsy occurred ‘without shoulder dystocia’ and that these infants had more fractured clavicles and were more likely to be permanently injured. Another explanation for their results is very possible. What if the operator experienced a shoulder dystocia and managed it by pulling hard on the infant’s neck to achieve delivery? In a retrospective review of hospital charts, that type of case would not be classified as ‘shoulder dystocia’ in this study because no other maneuvers were performed. The excessive neck traction could result in more fractures and permanent Erb’s palsy than occurs in infants who were managed by applying classic shoulder dystocia maneuvers.” 7

Dr. Allen replied to an AJOG article, Brachial Plexus Palsy: an in utero injury? (AJOG. Vol 181: No 5; part 1; pp 1271-72). “Because under-reporting of difficult deliveries is an acknowledged problem in labor management, reappraisal should focus more on objectively defining, properly managing and fully documenting shoulder dystocia.”

Gonik Theory

One researcher (Gonik), since 1999, has used dummy models and mathematical formulas, but never human or animal subjects. He ultimately concluded that “there is no direct application of these results to the clinical arena”.

Sandmire Theory

The Sandmire theory was based on his review and reinterpretation of the literature. He has performed no research and admits his opinions are based solely on “indirect evidence”. His theory, based on the absence of recording shoulder dystocia, speculates that once the baby’s body stops moving (stuck shoulder), some “unknown force” creates forward movement of the fetal head (the head pulls the body; aka the tractor-trailer theory). Johns Hopkins University researchers concluded that if it occurs at all, brachial plexus injury unrelated to the process of delivery is a rare phenomenon with little bearing upon the overall problem of shoulder dystocia at birth.

Arguments Against In Utero Causation

1. Only U.S. obstetricians believe that there is in utero causation

2. No neurology literature or texts support in utero causation

3. Uterine forces are in the upper two-thirds of the uterine muscle and not down low near the neck

4. In utero reports are frequently written by defense experts

5. In utero causation is based on:

a. Failure to record shoulder dystocia

b. the unproven theory that the infant’s head pulls its body during descent.

c. If it happens at cesarean section (that would be a traction force).

d. A pressure injury (there is no pressure injury on the overlying skin, fat, or muscle of the infant).

e. An injury to the posterior arm (no evidence for impact or

compression injury; (it is a traction injury).

6. Neurosurgical intraoperative findings have confirmed stretch injury.

7. Improved delivery techniques have reduced the injury rate fourfold.

8. Statistical analysis of in utero causation disproves the theory.

9. The injury rate is directly related to fetal size; the larger the baby, the greater the injury.

10. The injury rate is directly related to the number of maneuvers used to treat the dystocia.

11. Seventy-five percent to 90% of injuries occur in large babies.8

1. Sever, W. Obstetric paralysis; its etiology, pathology, clinical aspects and treatment, with a report of four hundred and seventy cases. Am J Dis Child 1916;12:541-78.

2. Jennett RJ, Tarby TJ, Krenick CJ. Brachial plexus palsy, an old problem revisited. AJOG 1992; 166; 1673-7.

3. Table 11.1 – Shoulder Dystocia References. Pg 1-5

4. Jennet’s first article: 1992- see 2 references not supporting his theories

5. Jennett’s most recent article [11] – Shoulder dystocia not recorded, it didn’t happen.

6. Admitted to ascertainment bias. Gherman.

7. Allen RH. Reply to in-utero: AJOG Volume 181: No. 5; part 1; pp1271-72

8. Dr, Dwight P Cruikshank, discussion of Gonik. The timing of congenital brachial plexis injury; A study of electromyelography findings in the newborn piglet : AJOG 1998; 176:688-95.

In Utero Causation Theories Used At Trial To Challenge Excessive Traction As The Cause of Brachial Plexus Injuries

A Review of the Evidence Based Literature in Shoulder Dystocia Litigation 1980’s – 2000’s Part 1