Beyond the Data — Understanding the Causes of Major Birth Defects: Steps to Prevention


Iskandar: Hello, I’m
Dr. John Iskandar, welcome to CDC Beyond the Data. I’m here today with
Dr. Allen Mitchell, Director of the Sloan
Epidemiology Center at Boston University. Allen, today we heard at
the Grand Rounds session about advances in
preventing birth defects. And, at both a public
health and a societal level, what’s the importance
of birth defects and birth defect prevention? Mitchell: Well, first let’s talk
about birth defects themselves, which occur in about one in
thirty three pregnancies, so it’s a fairly common
complication of pregnancy. And, among the category of
birth defects are a wide variety of specific birth defects. We think of congenital heart
problems, we think of problems of the abdominal
wall and so forth. But together, it accounts for about a 120 thousand
babies born each year with a birth defect. And, I think that over time,
because birth defects have been with us for so many
centuries, people have, sort of, come to think of them as an unavoidable
consequence of being pregnant. When in fact research has
recently shown in the last, maybe, thirty, forty, fifty years that some birth
defects are actually avoidable. And, that’s where the
research function comes in. Iskandar: So, moving from
simply counting birth defects to making some advances
in prevention, I know many of our viewers may
have been familiar with the, we’re talking terms of the
thalidomide tragedy of the 1960s where pregnant women taking
thalidomide had babies with often serious limb defects. What have we learned
through research since then about prevention
of birth defects? And what are some of
the gaps that remain? Mitchell: That’s
a good question. The thalidomide debacle in
the 60s, really as you said, brought public attention
to the problem. But in fact, it was in the
1940s when we first learned that the placenta,
which we used to think, would protect the fetus from any
kind of environmental problem. It turns out that congenital
rubella, or German measles, was identified in the 40s and that was the
first time something like an infection was shown to increase the risk
of birth defects. The thalidomide example
showed us that medications could
also cross the placenta and medications could also
cause devastating birth defects in certain circumstances. So that really began the era
of attention being focused on whether there were in fact
other agents in environment that might increase the
risk of birth defects. And, so by avoiding those agents
women could presumably reduce their risk of having a
baby with a birth defect. Iskandar: So one of the
things that you’ve studied through VAMPS or the
vaccines and medications in pregnancy surveillance
system, is whether there might be
medication or other types of exposures that could increase
the risk of birth defects. Could you tell us a little
bit about what that system is? What its goals are? And, what some of its
findings have been so far? Mitchell: Sure. VAMPS was designed
specifically, as you point out, to examine the risks,
or relative safety of medication taken in pregnancy
and that includes vaccines. So our focus has been on the
wide range of medications and vaccines but our particular
focus has been on vaccines or medications that
might be used in a public health emergency. And, a good example
of that was the 2009 and 2010 pandemic
with the H1N1 virus. That was a situation where the
government anticipated there would be a pandemic and
they asked the VAMPS team to study the safety of the
vaccine and the medications that might be used, the
antiviral medications that might be used to
prevent or treat influenza. Mitchell: Some of our findings
which were available only months after the epidemic was over,
revealed from the standpoint of birth defects, that
there was no increased risk for birth defects in general. And, the vaccine also
didn’t increase the risk of specific birth defects. Iskandar: So I think that’s
a very important answer because it provided, you
know, reassuring evidence of the safety of the pandemic
influenza vaccine in pregnancy in a very timely manner. More broadly than just
medications and vaccines, what are some other
environmental exposures that we’re now learning
about that are associated with birth defects
and particularly ones that might be controllable
or preventable? Mitchell: And, that’s a
very important focus is that certain causes
of birth defects and the vast majority
are unknown and we’ll talk more
about that I hope. But, there are certain causes which by controlling the
causes we can reduce the risk of birth defects and prominent
among those are obesity, which as everyone knows has
increased fairly dramatically in the United States. And, pre-gestational
diabetes or diabetes that are present
before pregnancy. That. Those two factors,
along with smoking are known to increase the risk
of birth defects. By controlling obesity,
by controlling blood sugar and certainly by reducing
smoking we can make substantial reductions in the
number of the children who are born with birth defects. Iskandar: So I think that’s
a very important perspective in that it, you know
we were earlier talking about medications and their
potential to increase risk for birth defects but the
underlying diseases themselves is better controlled, such
as diabetes may result in prevention of birth defects. So, what are those
next frontiers in birth defects prevention? Mitchell: Well, it’s
interesting that when I started out in this field which
was quite a while ago, the idea that some agent
could actually reduce the risk of birth defects. We knew about infections, we
knew about certain medications but the idea that something
simple might actually reduce the risk of birth defects
was unheard of. But research, and again research
in the area of birth defects, identified about 30 years
ago that a simple B vitamin, folic acid, could dramatically
reduce the risk of spina bifida and other defects of the spinal
cord called neural tube defect. And so we’re hopeful
that the horizon for birth defects prevention
includes both identifying other causes and if we’re lucky
identifying other factors which might if taken, such as
a B vitamin, reduce the risk of birth defects themselves. Iskandar: Thank you very much
for being with us today, Allen. Please join us again next
month for another episode of CDC’s Beyond the Data.

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