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Melanie Cole (Host): Mothers carrying a baby with myelomeningocele who choose fetal surgery for spina bifida, require the most expert and carefully managed care. My guest today is Dr. Michael Bebbington. He’s a Washington University Maternal Fetal Medicine physician, surgeon and Director of the Fetal Care Center at St. Louis Children’s Hospital. Dr. Bebbington, what an interesting topic we’re discussing today for other providers. Tell us a little bit about what myelomeningocele is. How common is it?

Michael Bebbington, MD, MHSc (Guest): It’s surprisingly common. Probably about one in 1000 pregnancies are complicated by what are called neural tube defects. And essentially what happens in the early development of the spine is that the lower part of the neural tube does not close and that leaves the developing nerve tissues in the spine exposed to damage in utero. 

Host: So, how does it fit into the umbrella of spina bifida which people have heard of maybe more often?

Dr. Bebbington: It’s essentially the same thing. 

Host: Okay so that’s interesting to note. Is there any way first of all, we’ve heard a lot about folic acid in the last 20 years and about reducing birth defects. Is there a way to prevent spina bifida?

Dr. Bebbington: So, the best strategy for prevention is supplementation with folic acid. The thing is that that has to be done for about three months before conception. And with most people not really planning their pregnancies, they don’t necessarily get a chance to benefit from the protective effect of extra folic acid. And what I try to recommend to all of my patients is that you take folic acid pretty much every day during the time that you are potentially going to be having children. 

Host: That’s important to note that even before you actually do get pregnant and you’re thinking about it, is even a good time to start. So, do we know the cause of this?

Dr. Bebbington: Well the cause is a complicated interaction of both genetic factors and what we call epigenetic factors which is sort of everything else in terms of environment. Obviously, there is a role for vitamin interactions which would fit into the epigenetic factors. But we are not able to identify a specific gene on a specific chromosome that is responsible for producing neural tube defects. 

Host: Well I certainly think it probably is multifactorial and genetic and racial, environmental as you said, nutrition. There are so many factors. How and when is it first detected?

Dr. Bebbington: So, the easiest way to detect early is with early ultrasound. And that can be as early as sort of 12-14 weeks of gestation. What’s more common though is moms or pregnant women should be getting a routine screening blood test that’s called a maternal serum alpha-fetoprotein and that’s done typically around 16 weeks of gestation. And alpha-fetoprotein is secreted from the open neural tube and that increases the concentration in the amniotic fluid and that increases the concentration in the mom’s blood stream. And so, that’s a really good sort of screening blood test for all pregnant women to get and it can be done early in gestation. 

More commonly though, when women come in the middle of the second trimester somewhere between 18 and 20 weeks for a detailed anatomy scan, then that gives them another opportunity for early detection of spina bifida. 

Host: At what point Doctor, should a mom be referred to a specialist such as yourself?

Dr. Bebbington: I would think that the best time to refer is as soon as it’s diagnosed. Because we can confirm that it is in fact the diagnosis and then can have discussions with the family about what the best course of management might be. 

Host: Let’s discuss that then, the best course of management and I know it’s certainly patient dependent but what do you tell them about treatment options that are available and what happens if surgery is not an option or not performed?

Dr. Bebbington: So, the commonest management would be what we basically call conservative management in which the diagnosis is confirmed, the pregnancy is followed closely with no interventions and then babies are delivered usually around 39 weeks of gestation by cesarean section and what that allows for is postnatal surgery to close the neural tube defect. That’s important that that gets done at a facility that is equipped to handle these sort of more complex pediatric neurosurgical interventions. 

Host: So interesting. So, who is eligible to undergo surgery?

Dr. Bebbington: So, it’s – there’s sort of a series of criteria that were established when we actually did the Mom’s Trial. The Mom’s Trial was a randomized controlled trial that was sponsored by the NIH comparing postnatal surgery to doing open fetal surgery for spina bifida. Surgery is clearly not for every family. If there are other abnormalities, if there are chromosomal abnormalities, anything that would expose a mother to increased risk of prematurity, complex maternal medical conditions that make them not good surgical candidates. So, this series of things that would make it so that surgery was not really a good idea for every family and in fact, we probably evaluate five or six families for every family that we offer surgery to. 

Host: What does it involve Dr. Bebbington? What is that open fetal surgery like for the families? How do you counsel them through this?

Dr. Bebbington: So, when they come for an evaluation visit, typically that’s a two or three day event where they undergo very detailed investigation with ultrasound, with fetal echocardiography and with fetal MRI. What that does it is allows us to look very carefully at the fetus to see if there’s any fetal indications that would make surgery not a good idea. 

They have a long counseling session with myself to go over what is spina bifida, what is the level of the lesion, how does that impact sort of growth and development of the nervous system for their particular baby? And then they meet with other members of our surgical team. So, with pediatric surgery, with pediatric neurosurgery, with neurology, with anesthesia; all of whom sort of provide perspective for the families on what the surgery involves so that they go into this fairly well informed about what they are undertaking. It is a major surgery not only because we are opening the mother’s abdomen, but we are also then opening the uterus to expose the baby’s back and allow the pediatric neurosurgeons to come in and do a closure of the defect. We then have to sew the uterus back up, make sure that it’s a watertight seal, reinfuse amniotic fluid, close the maternal abdomen and then about a four day postoperative recovery in hospital. 

But even after the surgery, the rest of the pregnancy is very much different than a normal pregnancy. Our moms go home on bedrest, on medications to try and minimize the risk of preterm labor. They are followed up every week. Most families in Missouri because Missouri is largely a rural state; will end up having to relocate into St. Louis for the duration of their pregnancy. And some centers where they are surrounded by larger metropolitan areas sometimes families can be allowed to go home and have their follow-up care done closer to home.

And then delivery electively at 37 weeks. Women after they go through this surgery can’t go through labor. We ask them not to get pregnant again for at least a two year period of time to allow for the two incisions that they end up with on their uterus to heal and even after that, every pregnancy that they have is at increased risk, not only for recurrence of spina bifida but for increased risk of problems with the uterine scars. 

Host: Wow. So, tell us a little bit about what you know about outcomes and prognosis and even what you tell women about future pregnancies and their risk as well. Kind of summarize all of this for us as to what happens after the fact and let other providers know what you would like them to know about spina bifida and when it’s so important to refer to your specialists. 

Dr. Bebbington: So, fetal surgery has three main benefits. One is that there is a reduction in the hindbrain herniation that typically accompanies an open neural tube defect and that’s where the cerebellum gets pulled down into the top of the spinal column as a result of the tethering of the spinal cord. That’s what produces the enlargement of the lateral ventricles inside the brain. So, reduction of that hindbrain herniation is a significant intrauterine event. 

One of the other problems with children that have spina bifida is that we have to often reestablish a way for the fluid to get out of the ventricles to decompress them and classically that has been done by using a VP shunt, so a tube that goes from the ventricles down into the abdomen. More recently, neurosurgeons have been using what’s called a third ventriculostomy as an alternative. But prenatal surgery, the fetal surgery decreases the risks of needing some sort of an intervention to help decompress the ventricles. 

So, if 80% of children that have neural tube defects need a shunt; those that have fetal surgery, that decreases to about 40%. And if you don’t have to have a shunt put in; you don’t have to have all of the shunt complications. 

And the third advantage is an improvement in neurologic function. So, by closing over the exposed developing nerve tissue; we can actually decrease the amount of damage that’s done in utero and improve neurologic function by up to two levels. Now that for many kids means that they will walk independently. And so there is a greater percentage of kids that walk independently as a result of having had the spinal surgery. 

What we counsel the moms about is that because of the nature of the incision on the uterus; it’s not like a cesarean section. The incisions are typically in the upper part of the uterus and those incisions don’t heal as strongly and so the risk not only during the initial pregnancy but every other pregnancy; there’s a risk that that scar may pull apart and cause a uterine rupture or uterine dehiscence. And the risks of that in and around the 20% mark in subsequent pregnancies. 

So, that’s why we advise mothers not to get pregnant again for at least two years to allow that incision to heal as well as it can before they embark on another pregnancy. And we always remind families that when you have had one pregnancy that’s be complicated by a neural tube defect; you are at an increased risk of having that happen again in a subsequent pregnancy. And much like the use of folic acid routinely, the best strategy that we have to try and prevent further recurrences is the use of folic acid but again in much higher doses. So, for a woman who has never had a pregnancy complicated by a neural tube defect; the amount of folic acid that’s in a regular prenatal vitamin pill is sufficient to provide protection and that’s somewhere in the order of 400 micrograms. 

For a family that has had a pregnancy with a neural tube defect; the supplementation needs to be in the order of 4 milligrams. So, a much higher dose that’s required to try and decrease the risk and that decrease is probably about 75%. So, it’s still a very, very, very effective intervention. 

Host: Do you have any final thoughts for other providers?

Dr. Bebbington: Prevention. I mean we have the capability to prevent a lot of these from happening and encouraging women to supplement routinely with a prenatal vitamin that contains folic acid is the best and most effective strategy. 

Host: Thank you so much Dr. Bebbington for joining us today. To consult with a specialist or to learn more about services offered at St. Louis Children’s Hospital please call Children’s Direct Physician Access Line at 1-800-678-HELP, that’s 1-800-678-4357. That wraps up another episode of Radio Rounds with St. Louis Children’s Hospital. Head on over to our website at www.stlouischildrens.org