What Is the “Maternal Forces” Defense in a Pennsylvania Erb’s Palsy Case?

Your child was born with an arm that would not move. Somewhere in the weeks that followed, someone told you it was nobody’s fault that the injury came from labor itself. Maybe the obstetrician said it. Maybe a letter did. Maybe a lawyer on the other side.

That explanation has a name. In courtrooms in Pittsburgh and across the Commonwealth it is called the maternal forces defense, and some version of it appears in nearly every Erb’s palsy case filed in Pennsylvania. It is not a medical finding about your delivery. It is a legal position about causation, and it is answerable.

What Is the Maternal Forces Defense?

The maternal forces defense argues that a newborn’s brachial plexus injury came from the natural forces of labor the mother’s contractions and expulsive efforts rather than from traction the delivering clinician applied. It concedes the child was injured while disputing that anyone is responsible. You will meet it in the answer to the complaint, again in a defense expert report, and at trial through a retained obstetrician or pediatric neurologist.

The argument is about physics, not conduct. No defense attorney will tell an Allegheny County jury that a mother injured her own child. What they will say is that the forces of an ordinary delivery can, on their own, stretch a nerve bundle past its limit.

Read closely, the position is narrower than it sounds. It rarely claims traction played no role. It claims the injury cannot be attributed to traction alone and therefore that a diagnosis, standing by itself, proves nothing about the care that produced it.

What Is Erb’s Palsy, and How Does It Happen During Delivery?

Erb’s palsy is an injury to the upper trunk of the brachial plexus, the nerve network running from the neck into the arm. It generally involves the C5 and C6 nerve roots, sometimes extending to C7, producing weakness or paralysis across the shoulder and arm. The brachial plexus arises from the C5 through T1 nerve roots and organizes into upper, middle, and lower trunks. Clinicians group these injuries under the broader term neonatal brachial plexus palsy, with Erb’s palsy describing the upper trunk pattern.

The mechanism is stretch. When the angle between a newborn’s neck and shoulder widens past what the nerves tolerate, the fibers give way. How badly they give way shapes the rest of the child’s life:

• Stretch injury — the nerve is pulled but stays intact, and function often returns
• Rupture — the nerve tears somewhere along its length
• Avulsion — the nerve root pulls away from the spinal cord entirely

Those are different injuries requiring different amounts of force. A permanently destroyed nerve is not the same case as a temporary stretch, and the causation argument should never be treated as though it were.

Why Do Defense Attorneys Rely on the ACOG Task Force Report?

In 2014, the American College of Obstetricians and Gynecologists published a task force report on neonatal brachial plexus palsy concluding these injuries can result from maternal forces, from clinician-applied forces, or from both. That finding is the foundation of the modern defense. Before that report, plaintiffs’ lawyers argued an Erb’s palsy diagnosis was itself evidence of negligence. The reasoning was tidy: nothing else could stretch a nerve that far. The task force declined to accept it.

The report also documented these injuries following deliveries where no shoulder dystocia was recognized, and deliveries by cesarean section. It identified associated risk factors, among them:

• Fetal malposition during labor
• Induction of labor
• Labor abnormalities
• Operative vaginal delivery
• A larger-than-average baby
• Shoulder dystocia

Defense counsel will put that report in front of the jury. What matters is what else it says.

Does This Defense Mean Our Case Will Fail?

No. The theory answers one question only whether the injury by itself proves negligence. It does not address whether risk factors were recognized, whether the delivery met the accepted standard of care, or whether an obstetric emergency was managed the way a competent physician generally would have. This is where families lose claims they should not lose. A parent hears the word unavoidable, accepts it, and never has the records read.

Pennsylvania malpractice claims rest on four elements: duty, breach of the standard of care, causation, and damages. The maternal forces theory speaks to one of them and leaves the standard of care untouched. Which means the questions that generally decide these cases are the ones it never reaches:

• Were known risk factors identified before delivery?
• Was a shoulder dystocia recognized when it occurred?
• Were accepted maneuvers performed, in a reasonable sequence?
• Was any of it written down at the time?

A claim built on those questions does not rise or fall on whether labor forces can theoretically injure a brachial plexus.

What Does the ACOG Report Say That the Defense Rarely Quotes?

The same report acknowledges that a clinician can increase strain across the brachial plexus by applying downward lateral traction to a newborn’s head. It also emphasizes contemporaneous documentation of how a dystocia was managed, and notes evolving research on delivery maneuvers.

A document stating that an injury may have more than one cause is not a document stating that a delivery was performed correctly. Three passages tend to help families.

• Traction still matters. The report accepts that downward lateral traction on the head increases stretch across the plexus. How the head was handled remains a live question.
• Documentation still matters. The report stresses accurate, contemporaneous notes describing how a dystocia was recognized and resolved. Thin or missing documentation is not a neutral fact.
• The science is still moving. The report noted research suggesting a benefit to prioritizing delivery of the posterior arm over first-line maneuvers findings that could shift what is expected of clinicians.

Defense experts quote the causation sentence. They quote these considerably less often.

How Does a Pennsylvania Court Decide Which Causation Experts May Testify?

Pennsylvania applies the Frye general acceptance standard rather than the federal Daubert test. Expert testimony resting on novel scientific evidence is admissible only where the methodology behind it is generally accepted in the relevant field. Courts examine method, not the conclusion drawn from it. Most national commentary on this defense discusses Daubert. In a Pennsylvania courtroom, that is the wrong test.

Pennsylvania Rule of Evidence 702 codifies that test, drawn from Frye v. United States, and the state Supreme Court reaffirmed the choice in Grady v. Frito-Lay. The inquiry targets methodology, and the party offering the testimony carries the burden.

The procedural vehicle is Pennsylvania Rule of Civil Procedure 207.1, which governs a motion to exclude expert testimony relying on novel scientific evidence. The court decides whether to take the question up before trial or defer it.

No Pennsylvania appellate court has squarely resolved whether the maternal forces theory clears that bar. It gets fought case by case, on the strength of a particular expert and a particular record.

Why Does Overstating a Case Backfire?

Courts have excluded testimony claiming a permanent brachial plexus injury can only result from clinician-applied traction and never from maternal forces. The more defensible opinion is narrower and record-specific: that labor forces alone are an unlikely explanation for this child’s particular injury. A federal court sitting in Pennsylvania dismissed a birth injury case on exactly this problem. The family’s experts testified the injury could only have come from the obstetrician’s traction and not from maternal forces. The court reviewed the literature, leaned on the ACOG report, and excluded them. That family had also failed to produce an expert defining the standard of care.

An absolute theory hands the defense a motion. A narrower one is far harder to exclude: that given the severity and pattern of this child’s injury, the course of this delivery, and the maneuvers recorded or conspicuously unrecorded, labor forces alone are an improbable explanation. That is an opinion about a record, not a universal claim about every birth.

What Does the Delivery Record Actually Show?

The labor and delivery file generally carries the case. Prenatal risk documentation, whether a dystocia was recorded, which maneuvers were performed and in what order, the head-to-body interval, and the pattern of nerve involvement all bear directly on the causation question.

The attorneys request the complete file, not the discharge summary. What they read it for:

• Prenatal records — documented risk factors, and whether anything was done about them.
• The delivery note — whether a dystocia was recognized and recorded as it happened.
• Maneuvers and sequence — which were attempted, in what order, and for how long.
• Head-to-body interval — the timeline the note may or may not capture.
• Nursing notes — frequently more candid than the physician’s summary.
• Neonatal and imaging findings — which nerve roots were involved, and how severely.

One detail carries unusual weight: which shoulder was affected. An injury involving the posterior shoulder, resting against the mother’s sacrum rather than behind her pubic bone, is harder to explain through downward traction on the head. It may point toward a different mechanism, and depending on the rest of the file can cut either way.

What Must a Pennsylvania Family Prove?

That a duty existed, that the provider breached the accepted standard of care, that the breach caused the injury, and that the family suffered damages. Each element is proven by a preponderance of the evidence, and qualified medical expert testimony is required in nearly every case. Those elements come from Hightower-Warren v. Silk and have not changed since.

Expert testimony is the real constraint. Pennsylvania’s MCARE Act sets who qualifies to testify about the standard of care. A standard-of-care expert generally must:

• Be substantially familiar with the standard of care for the specific care at issue.
• Practice in the same subspecialty as the defendant, or one with a substantially similar standard of care.
• Hold certification from the same or a similar board, where the defendant physician is certified.

A court may waive the subspecialty and board requirements where an expert has sufficient training through active involvement in a related field within the previous five years.

In practice, an obstetric case requires an obstetrician willing to read the chart honestly and say what they find. Locating that physician is the actual work, and the reason most firms decline these cases.

How Long Does a Pennsylvania Family Have to Act?

Generally two years, though children are treated differently. Pennsylvania does not count the period of minority against a child’s own claim, so that clock generally does not begin until the child turns eighteen meaning a claim can often be brought until roughly the twentieth birthday.

That protection comes from Pennsylvania’s tolling statute for minors, and it is more often misread than relied on. Two things families should know:

• A parent’s own related claims may run on a shorter timeline than the child’s.
• Records get archived, staff move on, and memories fade long before any legal deadline arrives.

Deadlines here turn on facts that are easy to misjudge from the outside. Whether time has run is better answered by having someone read the file than by reading a statute.

Contact Our Pittsburgh Erb’s Palsy and Birth Injury Attorneys

If your child was born with an arm that would not move and you were told nothing could have been done, John A. Caputo & Associates, P.C. will read the records and tell you honestly what they show. Call us for a free consultation, or reach us online. Our attorneys personally review every potential case when you call, you speak directly with a lawyer, not an intake coordinator. We represent families throughout Pittsburgh, Allegheny County, Western Pennsylvania, and across the Commonwealth.

We work on a contingency fee basis. You pay nothing unless we recover compensation for your family.

Frequently Asked Questions

Does the Maternal Forces Defense Apply if No Shoulder Dystocia Was Recorded?
It is often raised in exactly that situation. The literature includes brachial plexus injuries following deliveries where no dystocia was recognized, and the defense will rely on that. A missing dystocia note resolves nothing on its own — it makes the rest of the record more important.

Our Delivery Note Says Nothing About a Dystocia. Does That End Our Case?
Not necessarily. A dystocia that was not documented is not the same thing as one that did not occur. Nursing notes, the head-to-body interval, the newborn examination, and the pattern of injury all bear on what happened. Missing documentation is itself a fact worth examining.

Our Child Regained Some Movement. Is There Still a Claim?
Possibly, depending on what remains. Some of these injuries recover substantially and some do not, and the degree of lasting limitation generally shapes what a claim is worth. A child who regained partial function may still face permanent restrictions in strength and growth of the affected limb.

Who Can Serve as a Medical Expert Witness in a Pennsylvania Erb’s Palsy Case?
Pennsylvania’s MCARE Act generally requires a standard-of-care expert to be familiar with the care at issue, to practice in the same subspecialty as the defendant or one with a substantially similar standard, and to hold comparable board certification. Courts may waive some requirements.

Does It Matter Which of Our Baby’s Arms Was Injured?
It can. Whether the affected shoulder was the anterior one, lodged behind the mother’s pubic bone, or the posterior one, resting against her sacrum, bears on which forces could plausibly have reached that nerve bundle. It is one piece of a larger picture.

How Long Does Our Family Have to Bring an Erb’s Palsy Claim in Pennsylvania?
Pennsylvania generally does not count the years of a child’s minority against the child’s own claim, so that clock typically begins at eighteen. A parent’s related claims may run sooner. Because these timelines turn on specific facts, it is worth having the file reviewed rather than estimating.