Show me the Evidence
Obstetrics Study Leads to Changes in Practice and Guidelines
Researcher studies a common procedure, finds it is not effective
At a Glance
Who: Dr. William D. Fraser, University of Montreal
Issue: Meconium Aspiration Syndrome (MAS) is a life-threatening complication in late-term pregnancies. Amnioinfusion is a widely used treatment to prevent MAS; however, evidence of its effectiveness was limited.
Research: A CIHR-funded study by Dr. Fraser launched in 2003 included 1,800 women from 56 centres in 13 countries who had meconium-stained amniotic fluid.
Impact: As a result of Dr. Fraser's research, multiple medical associations around the world changed their guidelines for prevention of meconium aspiration syndrome.
Sources: Amnioinfusion for the Prevention of the Meconium Aspiration Syndrome. N ENGL J MED. 2005; Sep 1;353(9): 909–17.
Sometimes, advances in health care come not from newly developed treatments or technologies, but from finding out that a common procedure isn't as effective as once believed.
This is what happened when Dr. William D. Fraser began investigating the effectiveness of a treatment called amnioinfusion (AI). Amnioinfusion is a procedure used on certain women about to give birth to remove meconium from their amniotic fluid. Meconium is the earliest stool produced by an infant and is typically expelled shortly after birth.
When women have meconium in their amniotic fluid, meconium aspiration syndrome (MAS) can result. MAS, a life-threatening condition, occurs when amniotic fluid contaminated with meconium is inhaled by an infant either before or during birth. Meconium in the airway can lead to airway obstruction, lung or cardiovascular dysfunction, hypoxia (lack of oxygen), pneumonia or neurological effects.
The Evidence: Better Care
In response to Dr. Fraser's findings, the American College of Obstetricians and Gynecologists issued a statement saying AI is no longer a recommended procedure for meconium-stained amniotic fluid. Dr. Fraser's work answered a very important question and has led to a change of practice in many places worldwide.
"We know that babies normally practise breathing in utero. They're not breathing air but they're doing respiratory movements where fluid is moved up and down the airways. There is the potential for meconium to enter the airway before the baby takes its first breath," Dr. Fraser said. Dr. Fraser is an obstetrician and professor as well as Chair of the Department of Obstetrics and Gynecology at the University of Montreal.
Meconium is found in amniotic fluid in up to 22% of all deliveries.1 MAS occurs in anywhere from 2% to a third of these.2 AI is an intervention in which physicians infuse sterile fluid into the amniotic fluid surrounding the near-term infant in an attempt to dilute the concentration of meconium. The idea is that a diluted meconium would affect the infant's lungs less severely. It was a routinely used treatment in clinics around the world for the prevention of MAS in at-risk women.
However, "AI presents a potential risk to the mother. The technique involves the transfer of significant quantities of fluid through a catheter into the uterine cavity during labour," Dr. Fraser said. With the introduction of the fluid comes a possible increase in pressure within the amniotic cavity which could occasionally lead to a severe adverse event – amniotic fluid embolism, a potentially fatal condition for the mother.
And in Latin America and other parts of the world, the presence of meconium in the amniotic fluid was a leading cause of Caesarean sections – a procedure in its own right that puts mothers at increased risk of infection and other complications.
Back in the late 1990s, Dr. Fraser became aware that AI for the prevention of MAS lacked good quality studies proving its effectiveness. There were some studies that said it helped, but others that said it wasn't beneficial. But these studies tended to be small and didn't have the statistical weight to prove its effectiveness one way or another. The question was whether the procedure was truly beneficial, or whether it was adding an additional risk to mothers and their infants.
"Yet, at the time, the technique had been adopted by practitioners worldwide in an attempt to prevent MAS," he said.
According to Dr. Thomas Wiswell, prior to Dr. Fraser's study, practitioners were divided as to whether or not they thought AI was an effective approach.
"I'd work in one hospital one day and they'd say they never do AI because they believed the literature did not support it. The next day I'd be at a different hospital and all the obstetricians performed AI because they thought it was a good approach. It showed the divergence of opinions back in the 1990s," he said.
Dr. Wiswell is a professor of pediatrics at the University of Florida and also works as a newborn intensivist at Florida Hospital for Children in Orlando. There were no good, large studies proving its usefulness one way or the other, he said.
To solve this dilemma, Dr. Fraser launched a study in 2003 to determine whether or not AI was effective in the treatment of MAS. In order to get the statistical numbers needed, the study included 1,800 women from 56 centres in 13 countries who had meconium-stained amniotic fluid. That many countries needed to be included in order to get large enough numbers to be meaningful statistically, Dr. Fraser said.
Centres in Europe, South America, South Africa, the United States and Canada participated, making it a truly international effort. Results from the study were published in the prestigious New England Journal of Medicine in 2005, and demonstrated that AI is not effective in preventing MAS.
The study showed that cases with meconium in the amniotic fluid are equally likely to develop MAS regardless of whether AI is performed.
Within three years of the study being published, multiple medical associations around the world changed their guidelines, recommending that AI no longer be used as a way to prevent MAS. Among the first to change their guidelines were the American Academy of Pediatrics, the Neonatal Resuscitation Program, and the Society of Obstetricians and Gynaecologists of Canada.
Dr. Wiswell notes that after Dr. Fraser's study came out, the American College of Obstetricians and Gynecologists issued a statement saying AI is no longer a recommended procedure for meconium-stained amniotic fluid.3
"The authors commented that this trial really answered the question," Dr. Wiswell said. Dr. Fraser's work answered a very important question and has led to a change of practice in many places worldwide.
However, there is one caveat to the findings. Dr. Fraser points out that the study was performed in centres where electronic fetal heart rate monitoring (EFHRM) technology was used. EFHRM is used to monitor an infant's heart rate and can be an indicator of changes in oxygen status. The study clearly showed AI does not offer any advantage in centres where EFHRM is routinely used, but its role is still unclear in places where EFHRM is not available.
In fact, in some parts of the world where this monitoring device is not available, there may still be a role for AI. This is an area that still needs research, he said.
Canadian Neonatal Network
Dr. Fraser's work is part of a broader research effort in Canada to improve the care of newborns. CIHR funding helps support the Canadian Neonatal Network. To reduce costs and improve care, Network members share information about the type of care given and the outcomes of treatment. The Network links 27 neonatal intensive care units across Canada. New and significant findings have resulted from the Network's database. For instance, all newborns are routinely screened for a condition that can cause blindness, known as retinopathy of prematurity. Information collected by the Network has helped determine when screening is necessary, a change that will reduce costs by more than $1 million per year.4
The effects of this Canadian-led study were felt internationally. The research had the effect that a treatment that was not only ineffective but had rare, albeit serious complications ended up being removed from practice.
For Further Reading:
- Intrapartum assessment of the postdate fetus. Am J Obstet Gynecol. 1981; 141: 516–20.
- Canadian-led international study shows amnioinfusion does not reduce risk of meconium aspiration syndrome.
- Amnioinfusion does not prevent meconium aspiration syndrome. Obstet Gynecol. 2006; 108: 1053–5
- Evidence for changing guidelines for routine screening for retinopathy of prematurity. Arch Pediatr Adolesc Med. 2001; 155: 387–95.
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