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A ripple effect
It’s unusual for a single study to effect a major change in medical procedures, but that’s what happened after William Fraser’s research was published.
The Montréal-based obstetrician studied a procedure called amnioinfusion (AI), which had been commonly used in Canada and the United States to prevent a rare but life-threatening illness affecting newborns. Fraser found that the procedure was generally ineffective and unnecessary, considering that AI can cause other medical risks for the unborn child and discomfort for the expectant mother. The landmark finding led to significant widespread medical policy changes, and doctors stopped routinely using the treatment.
“AI was a good example of a technique that was introduced into medical care without a solid evaluation of its effectiveness,” says Fraser, who practises obstetrics at the Sainte-Justine University Hospital Centre and is chair of the department of obstetrics and gynecology at Université de Montréal’s faculty of medicine.
“One does not want to use a technique in routine care that carries a risk without being effective,” he says. AI can increase the risk of rare medical conditions, such as premature separation of the placenta.
This procedure was used for about 10 years in North America to reduce the risk of a condition called meconium aspiration syndrome (MAS), which can result when a newborn ingests meconium (baby stool sometimes present in the amniotic fluid) before or during birth. Meconium is sterile, but it can block the baby’s airways and cause chemical pneumonia if inhaled.
Meconium is present in the amniotic fluid in 7 to 22 percent of pregnancies that go to term. MAS is thought to occur in 2 to 36 percent of these cases. The AI procedure involves inserting a catheter into the amniotic fluid, then adding a sterile saltwater solution to dilute the meconium.
Fraser decided to study the treatment because there had been no large-scale research on its effectiveness despite its widespread use. He organized a team of researchers from 13 countries who studied nearly 2,000 pregnant women with thick meconium in their amniotic fluid. The study, published in the New England Journal of Medicine in 2005, found that women treated with AI had the same rates of MAS and perinatal death as untreated women. In the ensuing years, the finding has led medical bodies in Canada, the United States and other countries to recommend against the routine use of AI to prevent MAS, and that, in turn, has prompted doctors to make major changes in how they approach MAS.
Thomas Wiswell, a doctor at the Florida Hospital for Children who specializes in MAS, hailed the study as “a landmark work that has changed [pregnancy] management around the world.”
The episode, he says, is a good lesson for doctors. “The major lesson to be learned is that physicians should not be so willing to jump on the bandwagon for a therapy before it has undergone rigorous testing as to its efficacy.”
“Physicians need to practise evidence-based medicine despite having to deal with frightening disorders. Otherwise, we do our patients a disservice.”
While data on the use of AI in Canada before and after the study are not available, Wiswell says that the rate of AI has dropped to virtually nil in the United States. There, prior to the study, AI had been used in 60 to 80 percent of cases when babies were born with the presence of thick meconium. Today, the number is well under 5 percent.
Each year, worldwide, two to three million babies are born with thick meconium.
“Thanks to Fraser’s efforts, these infants no longer have to be subjected to AI,” says Wiswell, “There have been reported adverse effects of the therapy, so it was important to find out that it was not needed.”
Fraser’s study was supported by the Canada Foundation for Innovation through its funding of Université de Montréal’s perinatal clinical epidemiology unit, which provided the infrastructure to house the study’s personnel and data management.
In the years since the study, says Fraser, doctors have recognized that the presence of meconium in the amniotic fluid isn’t itself necessarily cause for treatment. Today, they focus on babies who are at greatest risk for MAS, looking for signs that they aren’t getting enough oxygen and then delivering them via Caesarean section.
Fraser’s study focused on women at facilities where fetal heart-monitoring equipment is available to detect whether a baby is in distress. He says more study is now needed on AI at facilities that don’t have such equipment.