Junkfood Science: The greatest myths of birth defects — Should unborn babies fear the environment?

February 09, 2007

The greatest myths of birth defects — Should unborn babies fear the environment?

One of the most heartbreaking situations is when a baby is born and something is wrong. The parents are in anguish as they search for a reason why. And they so often blame themselves or fear they did something to cause their baby harm. Similarly, throughout the pregnancy, expectant parents worry for their unborn baby and fear so many things could cause their baby to be born with birth defects.

Understanding the truth and the myths of birth defects is, perhaps, one of the greatest gifts we can give parents-to-be — both to help them know what they can do to help keep their baby safe and to lessen their stress by helping them understand when there is nothing plausible to worry about. Sound information can help ensure that pregnancy and new parenthood is a time of joy.

The medical experts who can give parents that information are those who’ve specialized in birth defects. They are known as dysmorphologists — although those of us who’ve been in neonatology since the dark ages may still know them as teratologists. Dysmorphology comes from the Greek words “dys” (which means abnormal) and “morph” (which means shape or form). Dysmorphologists study genetics and the factors that affect the normal growth and development of the fetus.

One of the world’s foremost dysmorphologists, spoke to the New Mexicans for Science and Reason on January 10th in Albuquerque. Dr. Jon Aase, M.D., of the Division of Clinical Genetics/Dysmorphology and Metabolism at the University of New Mexico Children’s Hospital, shared the top myths believed about birth defects. The title of his talk was “Dysmythology: Should unborn babies fear the environment?” His revelations were so astounding that parents, medical professionals and the public will find his expertise and decades of research of tremendous interest and help. Both he and Dave Thomas, president of the New Mexicans for Science and Reason, kindly extended their permission for this summary of his talk for readers of Junkfood Science.

Myth #1: Most birth defects are caused by environmental agents.

There are still unknowns about birth defects but what is known is often strikingly different from popular beliefs. The most believed fallacy about birth defects is that most are caused by environmental exposures, such as toxic chemicals, pollutants, radiation and other bad things. Heightening these scares is also popular among some environmental groups.

But amazingly, this is a myth. About 3% of babies are born with some type of congenital abnormality and most of those are single body system defects (club feet, heart defect) due to minor genetic factors and chromosomal aberrations. A very small percentage of birth anomalies — 1 in 500 births — are true “dysmorph” syndromes, or birth defects, which affect multiple systems of the body. And a tiny fraction of these (about 10%) are caused by environmental factors. But when dysmorphologists use the term “environmental” they are referring to any exposure in the environment of the unborn fetus.

Over recent decades, intense research has sought to identify possible environmental causes, called teratogens, for birth defects. In today’s climate of fears about our environment, few of us would probably think of drinking alcohol during pregnancy as an environmental factor, but it is the leading known cause for birth defects and mental retardation.

As the Centers for Disease Control and Prevention reports, fetal alcohol syndrome (FAS) affects multiple systems of the body resulting in characteristic facial features, growth disturbances and central nervous system problems. Just like autism, the spectrum of fetal alcohol disorders, now termed alcohol-related birth defects (ARBD), has broadened over the years and its prevalence varies depending on the population.

The key message is that fetal alcohol syndrome is completely preventable, said Dr. Aase. He helped to establish the Fetal Alcohol Syndrome Prevention Project in 1996 at UNM, a FAS/ARBD prevention effort in New Mexico. He said that the effect of alcohol isn’t linear, meaning it’s not necessarily related to the dose, the amount of alcohol a woman drinks during pregnancy. Any amount can result in FAS, making it important, in his experience, for women to not drink at all during pregnancy. Still, those who drink more are more likely to have a baby with FAS but that’s not guaranteed, either. The timing of the alcohol exposure during fetal development appears to be critical. But he also noted with sadness, a number of women have come to him thinking they needed to have an abortion because they’d had a drink before realizing they were pregnant and he said that there is no known case of FAS from a single drink.

And what about illicit drugs? Nope. Marijuana, cocaine, LSD or other hard drugs have not been shown to have teratogenic effects. Only alcohol.

Myth #2: Anything that causes birth defects in animals will cause birth defects in people.

These facts even astonished this audience of scientists. He reported that no human birth defect — either risk or type — has ever been predicted by animal studies. People are not rats or animals. In vitro studies have also failed to predict birth defects.

Myth #3: Any exposure to a known teratogen will cause a birth defect.

This is false. The only known thing to cause birth defects with any level of exposure — even a single dose — is thalidomide, which results in birth defects in 41% of cases. Quite a few medications are known to be capable of acting as teratogens, however, and Dr. Aase showed slides and described a number of those medications. But that is why it is important for women to talk with their doctors as soon as they know they are pregnant so that the risks of birth defects can be limited as much as possible by the choice and dosage of medications.

Dr. Aase explained there are a number of factors that influence the risk for teratogenicity: the timing during gestation (developmental stage) of the exposure, the dosage, the route, and the genetics of both the baby and mother.

Concerning route, he has never known a birth defect to result from skin exposure to any teratogen. The primary route of exposure is oral. A much smaller risk comes from inhaled teratogens and the primary one is toluene among workers working without protective gear and proper ventilation. There are also infectious teratogens, such as rubella (German measles), which causes deafness and microcephaly.

Myth #4: A teratogen will always cause a birth defect.

The fact is, he said, no agent is always teratogenic. Radiation, for example, can be teratogenic in extremely high doses such as therapeutic levels used to treat cancers. But diagnostic levels as in chest X-rays, dental X-rays and mammograms and low environmental levels have never been shown to cause birth defects.

An interesting discussion brought out several points that will be of special interest to those concerned about radiation and other environmental dangers. The 1986 nuclear reactor accident in Chernobyl resulted in radioactive contamination of air and land in regions of the former Soviet Union and Western Europe. The possibility of being exposed to radiation caused extreme anxiety, especially among pregnant women. So great were the fears that thousands of abortions were performed...needlessly.

Over the past twenty years prolific studies have been conducted to determine if the levels of radiation exposure for the population may have contributed to higher rates of birth defects, stillbirths or mental retardation. Incredibly, in sharp contrast to lay press and anecdotal stories, the scientific information shows no evidence that the radiation exposures of pregnant women from Chernobyl produced any harmful effects. Looking into the research after the meeting, uncovered the same conclusions in a review of the science in Teratology by Dr. Frank P. Castronovo, Jr. Ph.D., FASHP, at the Department of Health Physics and Radiopharmacology, Brigham and Women’s Hospital, Harvard Medical School, Boston.

The comprehensive review released in 2006 by the International Atomic Energy Agency, World Health Organization and United Nations Development Programme reported:

As of mid-2005, however, fewer than 50 deaths had been directly attributed to radiation from the disaster, almost all being highly exposed rescue workers, many who died within months of the accident but others who died as late as 2004 ... Dr. Burton Bennett, chairman of the Chernobyl Forum and an authority on radiation effects ... “This was a very serious accident ... however, we have not found profound negative health impacts to the rest of the population in surrounding areas, nor have we found widespread contamination that would continue to pose a substantial threat to human health, with a few exceptional, restricted areas.”

...no evidence or likelihood of decreased fertility has been seen among males or females. Also, because the doses were so low, there was no evidence of any effect on the number of stillbirths, adverse pregnancy outcomes, delivery complications or overall health of children. A modest but steady increase in reported congenital malformations in both contaminated and uncontaminated areas of Belarus appears related to better reporting, not radiation.

Dr. Fred A. Mettler, of the University of New Mexico and International Atomic Energy Agency, described the International Chernobyl Project conducted in 1990 to determine the health effects from the radiation exposures. “Up to 1990, fetal malformation data did not show evidence of a significant radiation related increase,” he reported. There are major fears surrounding this emotionally-charged issue, he said, but most scientific groups have determined that the evidence does not support there being health effects. There had been predictions that thyroid cancers would double, for instance, and “about 3% of children were found by palpation to have enlarged thyroids and 0.5% had nodules. But there was no statistical difference between clean and contaminated areas,” he said. [emphasis added]

A study by researchers at Karl Franzens University, Graz, Austria examined the effects of the radioactive fallout after the Chernobyl disaster among the population in southern Austria. They monitored over 66,000 births from 1985 to 1989 and found: “No significant changes in the incidence of birth defects, abortion rate, or counseling rate at pregnancy termination clinics were observed.”

Dr. Aase responded to questions about other environmental issues. Mercury and methylmercury, for example, caused birth defects among babies born to Japanese women in the 1950s after mercury wastes had been dumped into Minamata Bay contaminating the fish they had been eating for months to years. However, the dose they were exposed to was as much as 400 times higher than the natural methylmercury levels in the fish we eat. No birth defects have been shown from the low levels of mercury/methylmercury in our air and foods today.

Dioxin scares are ubiquitous, too, and one of the most heartbreaking results of myths about this environmental danger occurred after a massive dioxin accident in Sevesco,Italy in 1976. Many Seveso women had abortions because they were afraid that their children would be born with defects — but not one of the aborted fetuses had birth defects. The population has been since followed for decades and there have been no increases in birth defects, cancers or any other serious health problems.

Myth #5: Exposure at any time during a pregnancy will cause birth defects.

In truth, said Dr. Aase, the effects of varying teratogens occur in very narrow windows during the development of the fetus.

Myth #6: A father’s exposures can cause anomalies in his offspring.

They may also be a surprise, but fathers have no role in birth defects. And it’s not been for lack of researchers trying to find some link. Paternal exposure to Agent Orange, for instance, has been studied extensively and “there is not a single suggestion of a cause, relationship or risk,” said Dr. Aase. The main role fathers can play in birth defects, according to Dr. Aase, is to not drink during pregnancy to help the mother not be tempted to drink, either.

Myth #7: A single teratogenic agent can cause a wide variety of birth defects.

This is a popular myth. For instance, among a population of industrial workers exposed to a certain chemical if there is a cluster of different birth defects born to the workers, blaming the industrial chemical may seem intuitive. But it is false. Every teratogen causes its own, very specific syndrome.

Myth #8: Only exposures cause birth defects.

Deficiencies of certain things can cause birth defects, too. For example, one of the most significant deficiencies resulting in birth defects is folic acid. It causes abnormalities of the spinal cord such as spina bifida, and the brain, such as anencephaly. Folic acid has been added to all wheat, rice and corn products, then labeled “enriched,” and quickly increased folate levels in women of childbearing age. That was followed by a marked decline in babies born with birth defects. Women of childbearing age have also been encouraged to take vitamins with 400 mcg folic acid daily. By 2002, spinal cord birth defects had dropped 32% from levels of a decade earlier, according to the CDC.

However, just last month, the CDC reported that folate levels among women of childbearing age had dropped 16% in 2004 from 2000 levels. Some of that is attributed to women avoiding “enriched” flour breads and other baked goods, believing them to be unhealthy. They’ve been eating less bread in general to watch their weight and favoring “healthier” whole grain products that are not fortified with folic acid.

Myths have led countless new parents to be afraid when they didn’t need to be afraid, to respond in ways that could do more harm, and fail to do things that really could make a difference. And of course, how many public health policies have been misguided by myths, rather than following science?

Thank you, Dr. Aase, for making your life’s work something that has truly made a difference in the lives of generations of young families.

© 2007 Sandy Szwarc

Photo of Dr. Aase courtesy of David Thomas, New Mexicans for Science and Reason

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