by Mary J. Dufton
Dr. Gregory Ryan, a Maternal Fetal Specialist at Mount Sinai Hospital in Toronto talked about the significant health impacts and risks for both the mother and infant from having surgery for the management of mylomeningocele. Although the surgery holds promise, further investigation is needed to examine ways to make the procedure easier and less invasive for both.
According to current figures, 1,500 babies are born each year with spina bifida. However, since Health Canada does not contribute to the data, it records the official number as 240 babies per year.
Folic acid supplements are critical for reducing the incidence of neural tube defects. All pregnant women and women considering becoming pregnant should take small doses of folic acid. A woman in a higher risk group should be taking a higher dose of folic acid, ideally before she becomes pregnant or as soon as she realizes she is.
In Canada, folic acid has been added to white flour, pasta and corn meal products -- since 1998. This has had a dramatic impact with a 50 per cent reduction in the incidence of neural tube defects since this initiative. Many other countries have had the same results.
Neurological conditions occur for two reasons. The first is the failure of the neural tube to form. The second is the negative effect of the amniotic fluid.
An examination of the significant health impacts of spina bifida were the rationale for examining strategies to reduce some of the damage caused by this condition.
Obstetricians have two patients, the mother and the baby. What is done for one has many safety implications for the other. Implications for future pregnancies after the surgery have to be considered.
Dr. Ryan says that up until now, foetal surgeries were always done if the baby’s or mother’s life was in danger. He thinks great strides have been made in fixing these conditions.
Although spina bifida is not a lethal condition, experts believed there was a role for the MOM trial in improving the health effects of babies born with spina bifida. However, much scepticism remained about the role of this particular intervention.
“By fixing the lesion, can the pressure be removed to allow the brain to return to its normal state?” Dr. Ryan asked. “It's a unique trial. There are approximately twenty-five major foetal therapy centres. There are three in Canada -- Vancouver, Montreal and Toronto -- and there are several in the United States. These centres are all pushing to develop new techniques.
“The collaboration was unique because everyone else stepped back from the procedure until there was proof that it worked. Three centres were identified -- California (UCSF), CHOP (Children's Hospital of Philadelphia) and Vanderbilt. The statistics would be reviewed at George Washington and overseen by the ICSD. The goal was to compare the safety and effectiveness of operating on the pregnant woman compared to the standard surgery which is performed on the baby after it is born.”
Two hundred pregnant women were studied. One hundred and eighty-seven were recruited. The primary outcome was fetal or neo-natal death and then the requirement for a shunt at the age of 12. The secondary outcomes were that some of the infant’s developmental skills were affected. The results of the trial were viewed with some scepticism.
The criteria were strict. The resident could not live outside of the United States. . Women and their families were required to travel to one of the centres identified, it would be determined whether or not the surgery would take place and the baby would be followed for the first year and a half.
A very detailed evaluation took place in order to assess the parents’ suitability for the procedure. All of the imaging would be repeated; there would be various psychological testing, lots of meetings with many members of the teams in order for the parents to be well aware of what they were doing – the pros, cons and particularly the potential risks.
Up until they were discharged, the mothers who were having the surgery prenatally would be admitted to the centre where the surgery would be done and those families would stay close by those centres for the whole pregnancy. The babies would be delivered at thirty-seven weeks by caesarean section, if they hadn't gone into labour before then.
The group that were not given the intervention would return to their own centres and they would return to have their babies and the required post-natal surgery. Essentially, the country was divided into three parts. The west went to the University of San Francisco, California Medical Center, the northeast went to the Children’s Hospital of Philadelphia and the southeast went to Vanderbilt University Medical Center in Tennessee.
When the babies reached their first year, their urological and developmental functioning was studied through looking at images of their brains and spines. Further similar tests were conducted when they reached thirty months.
According to Dr. Ryan, “Over five hundred women were excluded from the trial for various reasons, which delayed the progress of the trial. It was proposed that the trial should be completed in approximately two to two and a half years time. This was a real lesson to us, as it took the best part of ten years before the trial could be finished.”
The health risks from the pre natal surgery include separation of the membrane during in-utero procedures, e reduction in amniotic fluid and resulting complications. Rupture of the membrane was almost totally restricted to the pre-natal surgery and so was spontaneous premature labour.
Heart rate complications may arise during the repair, but tend to be minor because the group that has surgery would deliver at much earlier gestations than the group that did not have surgery. For very early delivery, conditions such as respiratory distress syndrome, infection, necrotizing enterocolitis, bleeding in the brain occur at a much higher rate in early deliveries. They decrease in deliveries that are closer to term.
Dr. Ryan notes that although survival is improving significantly beyond twenty-four weeks, any procedure that might cause premature delivery may be causing a problem that didn’t exist previously.
“In looking at the trial, the group delivered early had more respiratory distress syndrome. For babies that reached a year of age, all of these outcomes were worse in the post natal surgery groups; the need for a shunt was higher in post natal surgery, any placement of a shunt, any hindbrain herniation or any hindbrain kinking was higher in this group, which was something of a surprise. When we looked at the outcome at thirty months, there was a higher chance of that child walking independently in the prenatal surgery group.”
Pre-natal surgery before twenty-six weeks decreased the risk of death or the need for shunting by the age of twelve months. Scores on both intellectual and motor function improved along with the degree of hindbrain herniation, which is associated with the Chiari II malformation and the motor dysfunction.
There is a need to be very cautious where this surgery is concerned. The potential benefits must be higher than the risk of pre-maturity and the risk to the mother herself. Any pre-natal intervention increases the risk of pre-term births. There are risks to future pregnancies, the scar opening up and risks to the mother needing a blood transfusion. The statistics may be small, but these are major complications when they occur. And the health risks to a baby born prematurely are very significant.
Uuterine rupture is potentially catastrophic and fatal for the mother and baby in a future pregnancy because whenever the abdomen is weakened there is a risk of rupture.
And the risks are known to occur with previous caesarean sections.
“There is a risk of about 0.5 per cent in future pregnancies.” Dr. Ryan says.” If we do a classical caesarean section, the risks are significantly higher, over 5 per cent and the risk of a hysterectomy in future pregnancies is much higher. If the mother at some time has uterine surgery, then this also increases the risk of the scar opening up when she is again pregnant.”
Although the trial has shown important benefits, it remains controversial as it is still in its early stages.
Although the surgery showed promise, doctors in many countries favour a much less invasive approach to repair the neural tube and minimize the risks of premature labour of the baby and future complications for the mother.
What is next for the MOM trial? There's research examining pre-natal neuro stem cells in the role of spina bifida. This involves taking a cell that has essentially developed and inserting it into foetal tissue at a critical period so it develops as normal tissues. There is as an animal trial with three groups; one group had standard post natal care, one group had pre-natal intervention and the third group had standard surgical repair with the inclusion or neuro stem cells. The group that had the neuro stem cells appeared to show some potential benefits in that the neuro stem cells took over the function of the cells that had been damaged.