Most obstetric malpractice is due to medical system failures rather than intentionally made, incorrect decisions. System failures (more informally called “slipping through the cracks”) occur when a patient receives, or fails to receive, needed care due to inadvertence. Patients are at the greatest risk for system failures when they have nonserious conditions that are routinely managed without ongoing evaluation. System failures usually involve overlooking unexpected data. This might be ignoring the third call back by the mother of a child with an infected throat, which should have triggered a reevaluation of the patient’s treatment. This is not usually a problem because most children with infected throats have no major problem. It is the child with meningitis injured when the physician inadvertently continues routine treatment whose injuries lead to litigation.

In obstetrics, common system failures include failing to diagnose existing systemic diseases, failing to offer screening tests at the appropriate time, failing to act on positive test results, and failing to respond quickly to threats to fetal or maternal health. System failures pose the major risk in obstetric care because most pregnant women are healthy and most pregnancies end in the birth of a healthy baby.

Since the medical component of prenatal care is a screening program, failures in the prenatal care system are irrelevant to most women because they do not have any of the conditions for which the screening is performed. As with the child with an infected throat, the system failure harms only the patient who does not have the usual condition. In obstetrics, the failure of the prenatal system does not matter for most women; it does matter for a woman who has a medical condition that requires nonroutine treatment to protect her health or the health of the baby.

To use the MSAFP example assume the physician has all abnormal laboratory reports put on the front of the chart for review. The file clerk loses 2% of all laboratory reports. Since the physician depends on abnormal results being flagged, no flag is taken to be a normal result.

Assuming a rate of 1 neural tube defect per 500 births, the probability of a missed diagnosis is .02 × .002, or 1 per 25,000 births. The odds are that this practice could go on for years before resulting in an injury in any given physician’s practice. That injury can be very expensive. A $1 million award would not be unusual in such a case. Assume further that an average obstetrician delivers 50 babies a year. (This is a low number for a full- time obstetrician but is used to include family practitioners who deliver babies and physicians with substantial gynecology practices.) Then 25,000 births represent 500 obstetrician-years, for a risk of $2,000 per obstetrician-year.

From a management perspective, delivering routine obstetrical services is more like flying an airliner than like treating an acute illness: small things matter, and mistakes are infrequent but costly. As with flying the airliner, most of the things that matter are not done by the person in charge. The pilot does not service the engines, and most prenatal care is done by persons other than the supervising physician.