Questions about Prenatal Ultrasound and the Alarming Increase in Autism

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Questions about Prenatal Ultrasound and the Alarming Increase in

Autism

by Caroline Rodgers

© 2006 Midwifery Today, Inc. All rights reserved.

[Editor's note: This article first appeared in

Midwifery Today Issue 80, Winter 2006.]

In May 2006, figures from the Centers for Disease Control (CDC) confirmed

what too many parents and educators already knew: The incidence of autism

is high, making it an " urgent public health issue, " according

to Dr. José Cordero, director of the CDC's National Center on Birth

Defects and Developmental Disabilities. Only 12 years ago autism spectrum

disorder (ASD) was so rare that it occurred in just one in 10,000

births.(1) Today ASD, which is characterized by a range of learning and

social impairments, now occurs in one in 166 children (2)­with no sign of

leveling off.

The steep increase in autism goes beyond the US: It is a global

phenomenon, occurring in industrialized nations around the world. In the

UK, teachers report one in 86 primary school children has special needs

related to ASD.(3)

The cause of autism has been pinned on everything from " emotionally

remote " mothers (since discredited) to vaccines, genetics,

immunological disorders, environmental toxins and maternal infections.

Today most researchers theorize that autism is caused by a complex

interplay of genetics and environmental triggers. A far simpler

possibility worthy of investigation is the pervasive use of prenatal

ultrasound, which can cause potentially dangerous thermal

effects.

Health practitioners involved in prenatal care have reason to be

concerned about the use of ultrasound. Although proponents point out that

ultrasound has been used in obstetrics for 50 years and early studies

indicated it was safe for both mother and child, enough research has

implicated it in neurodevelopmental disorders to warrant serious

attention.

At a 1982 World Health Organization (WHO) meeting sponsored by the

International Radiation Protection Association (IRPA) and other

organizations, an international group of experts reported that

" [t]here are several frequently quoted studies that claim to show

that exposure to ultrasound in utero does not cause any significant

abnormalities in the offspring. …However, these studies can be criticized

on several grounds, including the lack of a control population and/or

inadequate sample size, and exposure after the period of major

organogenesis; this invalidates their conclusions…. " (4)

Early studies showed that subtle effects of neurological damage linked to

ultrasound were implicated by an increased incidence in left-handedness

in boys (a marker for brain problems when not hereditary) and speech

delays.(5) Then in August 2006, Pasko Rakic, chair of Yale School of

Medicine's Department of Neurobiology, announced the results of a study

in which pregnant mice underwent various durations of ultrasound.(6) The

brains of the offspring showed damage consistent with that found in the

brains of people with autism. The research, funded by the National

Institute of Neurological Disorders and Stroke, also implicated

ultrasound in neurodevelopmental problems in children, such as dyslexia,

epilepsy, mental retardation and schizophrenia, and showed that damage to

brain cells increased with longer exposures.(7)

Dr. Rakic's study, which expanded on prior research with similar results

in 2004 (8), is just one of many animal experiments and human studies

conducted over the years indicating that prenatal ultrasound can be

harmful to babies. While some questions remain unanswered, based on

available information, health practitioners must seriously consider the

possible consequences of both routine and diagnostic use of ultrasound,

as well as electronic fetal heart monitors, which may be neither

non-invasive nor safe. If pregnant women knew all the facts, would

they choose to expose their unborn children to a technology that­despite

its increasingly entrenched position in modern obstetrics­has little or

no proven benefit?

Problems with Sound and HeatOne challenge that

ultrasound operators face is keeping the transducer positioned over the

part of the fetus the operator is trying to visualize. When fetuses move

away from the stream of high-frequency sound waves, they may be feeling

vibrations, heat or both. As the FDA warned in 2004, " ultrasound is

a form of energy, and even at low levels, laboratory studies have shown

it can produce physical effect in tissue, such as jarring vibrations and

a rise in temperature. " (9) This is consistent with research

conducted in 2001 in which an ultrasound transducer aimed directly at a

miniature hydrophone placed in a woman's uterus recorded sound " as

loud as a subway train coming into the station. " (10)

A rise in temperature of fetal tissue­especially since the expectant

mother cannot even feel it­might not seem alarming, but temperature

increases can cause significant damage to a developing fetus's central

nervous system, according to research.(11) Across mammalian species,

elevated maternal or fetal body temperatures have been shown to result in

birth defects in offspring.(12) An extensive review of literature on

maternal hyperthermia in a range of mammals found that " central

nervous system (CNS) defects appear to be the most common consequence of

hyperthermia in all species, and cell death or delay in proliferation of

neuroblasts [embryonic cells that develop into nerve cells] is believed

to be one major explanation for these effects. " (13)

Why should neurodevelopmental defects in rats or other mammals be of

concern to expecting women? Because, as Cornell University

researchers proved in 2001, brain development proceeds in the same manner

" across many mammalian species, including human infants. " (14)

The team found " 95 neural developmental milestones " that helped

them pinpoint the sequence of brain growth events in different

species.(15) Therefore, if repeated experiments show that elevated heat

caused by ultrasound damages fetal brains in rats and other mammals, one

can logically assume that it can harm human brains, too.

In fact, the FDA and professional medical associations know that prenatal

ultrasound can be dangerous to humans, which is why they have

consistently warned against the non-medical or " keepsake "

ultrasound portrait studios that have cropped up in malls throughout the

country.(16)

The risks to the baby are potentially higher in commercial enterprises

due to the higher acoustic output required for high-definition images, a

potentially long session­as technicians hunt for suitable images­and the

employment of ultrasound operators who may have no medical background or

appropriate training. These variables, along with factors such as

cavitation (a bubbling effect caused by ultrasound that can damage cells)

and on-screen safety indicators that may be inaccurate by a factor

ranging from 2–6 (17), make the impact of ultrasound uncertain even in

expert hands. Quite simply, if ultrasound can injure babies, it can cause

the same damage whether done for routine, diagnostic or

" entertainment " purposes.

Elevated Maternal Temperatures Cause Birth

DefectsUnderstanding what happens when the fetus's temperature

increases, whether caused by an elevation in maternal core temperature or

by the more local effect of ultrasound, is the key to appreciating

prenatal ultrasound risks. An individual's body temperature varies

throughout the day due to various factors such as circadian rhythms,

hormone fluctuations and physical exertion. While people may have up to

1.5° F in each direction of what is considered a " normal " core

temperature, the overall average among people is 98.6° F. An increase of

only 1.4° F to 100° F can cause headaches, body aches and fatigue, enough

to get the individual excused from work. A temperature of 107° F can

cause brain damage or death.

A core temperature of about 98.6° F is important because that is the

point at which many important enzyme reactions occur. Temperature affects

the actual shape of the proteins that create enzymes, and improperly

shaped proteins are unable to do their jobs correctly. As factors such as

the amount of heat or duration of exposure increase, enzyme reactions

become less efficient until they are permanently inactivated, unable to

function correctly even if the temperature returns to

normal.(18)

Because temperature is critical to proper enzyme reactions, the body has

built-in methods to regulate its core temperature. For instance, when it

is too low, shivering warms it up; when it is too high, sweating wicks

off the heat. For obvious reasons, fetuses cannot cool off by sweating.

However, they have another defense against temperature increases: Each

cell contains something called heat shock (HS) proteins that temporarily

stop the formation of enzymes when temperatures reach dangerously high

levels.(19)

Complicating the issue is the fact that ultrasound heats bone at a

different rate than muscle, soft tissue or amniotic fluid.(20) Further,

as bones calcify, they absorb and retain more heat. During the third

trimester, the baby's skull can heat up 50 times faster than its

surrounding tissue (21), subjecting parts of the brain that are close to

the skull to secondary heat that can continue after the ultrasound exam

has concluded.

Elevated temperatures that might only temporarily affect the mother can

have devastating effects on a developing embryo. A 1998 article in the

medical journal Cell Stress & Chaperones reported that " the HS

response is inducible in early embryonic life but it fails to protect

embryos against damage at certain stages of development. " The

authors noted, " With activation of the HS response, normal protein

synthesis is suspended…but survival is achieved at the expense of normal

development. " (22)

Autism, Genetics and Twin StudiesWhat does elevated

body temperature have to do with autism? Geneticists are trying to

crack the DNA mysteries behind ASD. Recently researchers linked two

mutations of the same X chromosome gene to autism in two unrelated

families, although they do not yet understand at what stage these genes

were damaged.(23) Because sibling and twin studies show a higher

prevalence of autism among children in families with one autistic child,

geneticists expected to find inherited factors, but despite millions of

dollars invested in the search, no clear explanation indicates that ASD

is inherited. Perhaps scientists need look no further than at the thermal

effects of ultrasound for many answers.

If prenatal ultrasound is responsible for some cases of autism, it stands

to reason that if one twin were autistic, the other would have a high

probability of being affected, since both would have been exposed to

ultrasound at the same time. In both identical and fraternal twins, one

twin could be more severely affected than the other if he or she happened

to take the brunt of the heat or sound waves. In the case of fraternal

twins, since autism strikes males between three to five times more often

than females, the sex of the twins also could make a difference in

outcome.

A 2002 study showed that simply being a twin substantially increased the

likelihood of autism, making twinning a risk factor.(24) Could this

increased twin risk factor have to do with the practice of giving mothers

with multiple gestations more ultrasounds than those expecting single

births? While not discounting the role genetics may play in autism,

the possible impact of prenatal ultrasound deserves serious

consideration.

Ultrasound Warnings UnheededThe idea that a prenatal

ultrasound can be hazardous is not new. The previously mentioned 1982 WHO

report, in its summary " Effects of Ultrasound on Biological

Systems, " stated that " …animal studies suggest that

neurological, behavioral, developmental, immunological, haematological

changes and reduced fetal weight can result from exposure to

ultrasound. " (25)

Two years later, when the National Institutes of Health (NIH) held a

conference assessing ultrasound risks, it reported that when birth

defects occurred, the acoustic output was usually high enough to cause

considerable heat.(26). Although the NIH has since stated that the report

" is no longer viewed…as guidance for current medical practice, "

the facts remain unchanged.

Despite the findings of these two major scientific gatherings, in 1993

the FDA approved an eight-fold increase in the potential acoustical

output of ultrasound equipment (27), greatly increasing the possibility

of disastrous pregnancy outcomes caused by overheating. Can the fact

that this increase in potential thermal effects happened during the same

period of time the incidence of autism increased nearly 60-fold be merely

coincidental?

Hot Tubs, Steam Rooms, Saunas and Maternal

FeversIf the culprit is heat, then what about other

situations in which heat impacts pregnancy? A 2003 study titled,

" A report of heat on embryos and fetuses " in the International

Journal of Hyperthermia states, " hyperthermia during pregnancy can

cause embryonic death, abortion, growth retardation and developmental

defects. " (28) It further states, " An elevation of maternal body

temperature by 2 degrees Centigrade [3.6 degrees Fahrenheit] for at least

24 hours during fever can cause a range of developmental

defects. " (29) The report noted that necessary data to draw

conclusions on exposure times less than 24 hours were lacking (30),

leaving open the possibility that elevated maternal temperatures for

shorter periods may adversely affect fetuses.

A study reported in the Journal of the American Medical Association

(JAMA) found that " women who used hot tubs or saunas

during early pregnancy face up to triple the risk of bearing babies with

spina bifida or brain defects. " (31). Hot tubs and baths present

greater dangers than other heat therapies such as saunas and steam rooms

because the immersion in water foils the body's attempt to cool off via

perspiration, in much the same way fetuses cannot escape elevated

temperatures in the womb.

All of this taken together establishes the fact that heat, whether caused

by elevated maternal temperature or by an ultrasound transducer that

remained over one area too long, can set into motion damaging changes in

a developing baby. Using common sense, why would anyone think that

intruding upon the continuous, seamless development of the fetus, which

has for millions of years completed its work without assistance, be

without consequences?

Vaccine and Thimerosal ControversyDespite

long-standing evidence that ultrasound induces thermal effects and that

thermal effects can harm fetal brain development, the cause of autism has

remained so elusive to researchers that many autism societies use a

puzzle piece as part of their logos. Particularly confounding is the fact

that ASD plagues the children of high-income, well-educated families who

have the best obstetrical care money can buy. Why would women who took

their prenatal vitamins, observed healthy diets, refrained from smoking

or drinking and attended all regularly scheduled prenatal visits bear

children with profound neurologically based problems?

Some believe that childhood vaccines, at first available only to

those who could afford them, cause autism. Many vaccines contained

thimerosal, a mercury-based preservative, which was thought to have a

cumulative neurotoxic effect on children, especially as the number of

childhood vaccines increased during the same period of years that the

prevalence of autism increased. However, after an exhaustive review in

1999, the FDA found no evidence of harm in the use of thimerosal in

childhood vaccines.(32)

Despite those findings, that same year the FDA, NIH, CDC, Health

Resources and Services Administration (HRSA) and American Academy of

Pediatrics (AAP) together urged vaccine manufacturers to reduce or

eliminate thimerosal in childhood vaccines.(33) Pharmaceutical companies

complied, and ultimately reduced the infant thimerosal exposure by

98%.(34)

Interestingly, not only did autism rates fail to decrease, they continued

to increase. ASD increases are between 10 to 17 percent every year,

according to the Autism Society of America (35), indicating that

thimerosal is not to blame.

Thimerosal was not the only area of concern in the vaccine-autism

controversy. Many people believed that a correlation existed between the

triple vaccine MMR (mumps, measles and rubella) and ASD. However, a

large, retrospective epidemiological study of more than 30,000 children

in Japan between 1988 and 1996 found that the autism rate continued to

climb after the vaccine was withdrawn.(36) Those results were no

different than the outcome of a 1999 study published in The Lancet, that

showed no corresponding jump in autism in the UK after the introduction

of the MMR vaccine.(37)

A 2001 study published in JAMA examining California autism and MMR

vaccination rates said the results did " not suggest an association

between MMR immunization among young people and an increase in autism

occurrence. " (38) While concerns about vaccines and mercury exposure

should not be dismissed, evidence to date does not implicate either one

as a major factor in the explosion of ASD cases.

Global Autism EpidemicStatistics on the increase of

autism worldwide among industrialized nations show that it has emerged in

just the last few decades across vastly different environments and

cultures. What do countries and regions with climates, diets and

exposure to known toxins as disparate as the US, Japan, Scandinavia,

Australia, India and the UK have in common? No common factor in the

water, air, local pesticides, diet or even building materials and

clothing can explain the emergence and relentless increase in this

serious, life-long neurodevelopmental disorder.

What all industrial countries do have in common is the quiet yet

pervasive change in obstetrical care: All of them use routine prenatal

ultrasound on pregnant women.

In countries with nationalized healthcare, where virtually all pregnant

women are exposed to ultrasound, the autism rates are even higher than in

the US, where due to disparities in income and health insurance, some 30

percent of pregnant women do not yet undergo ultrasound

scanning.

The Changes in UltrasoundIn considering initial studies

indicating that prenatal ultrasound is safe, one must factor in the ways

in which the technology and its applications have continually changed and

how that has altered the potential exposure of unborn children. Besides

the huge increase in allowable acoustic output in the early 1990s, the

following changes have made the field of prenatal ultrasound riskier than

ever:

The number of ultrasound scans conducted during each pregnancy has

increased, with women often receiving two or more scans even in low-risk

situations.(39) Women in " high-risk " situations may receive

many more scans­which, ironically, may raise their risk. The range of time within an embryo or fetus's development when

ultrasound is performed has extended to very early in the first trimester

and continues into the third trimester, right up to delivery. Fetal heart

monitors that are used prior to delivery­sometimes for hours­have not

been shown to reduce neurological problems and may increase them.(40) The development of the vaginal probe, which positions the beam of

sound much closer to the embryo or fetus, may put it at higher risk. The use of Doppler ultrasound, which is used to study blood flow or

to monitor the baby's heartbeat, has increased. According to the 2006

Cochrane Database of Systematic Reviews, " routine Doppler ultrasound

in pregnancy does not have health benefits for women or babies and may do

some harm. " (41)

Increasingly Common Birth DefectsDr. Rakic's research

team, cited earlier in this article for its recent study on mouse brains

and ultrasound, pointed out that " the probe was held stationary for

up to 35 minutes, meaning that essentially the entire fetal mouse brain

would have been continually exposed to the ultrasound for 35 minutes…in

sharp contrast to the duration and volume of the human fetal brain

exposed by ultrasound which will typically not linger on a given tissue

volume for greater than one minute. " (42) This is an excellent point,

which is worth pursuing.

One of the most popular non-medical uses of ultrasound, which can extend

a medically indicated session, is to determine the sex of the baby.

Could this have a connection to the increase in birth defects

involving the genitals and urinary tract? The March of Dimes says

that these types of birth defects affect " as many as 1 in 10

babies, " adding that " specific causes of most of these

conditions is unknown. " (43)

Following this line of thought, consider what other parts of the body are

scrutinized by ultrasound technicians, such as the heart, where serious

defects have soared nearly 250 percent between 1989 and 1996.(44) The

list of unexplained birth defects is not a short one, and in light of

what is emerging about prenatal ultrasound, scientists should take

another look at all recent trends, as well as the baffling 30% increase

in premature births since 1981, now affecting one in every eight children

(45), with many showing subsequent neurological damage.(46)

Although many claim that ultrasound benefits outweigh the risks, that

statement has no basis and much evidence is to the contrary. A large

randomized trial of 15,151 pregnant women, conducted by the RADIUS Study

Group, found that in low-risk cases, high-risk subgroups and even in

cases of multiple gestations or major anomalies, the use of ultrasound

did not result in improved outcome in the pregnancies.(47) The argument

that ultrasound is either reassuring to the parents or provides an early

opportunity for bonding pales in the face of the possible risks that are

emerging as new data become available. Parents and health practitioners

may not be able to easily turn away from this window on the womb and

resume more traditional practices in obstetrics and midwifery. However,

with the disturbing trend in autism and other equally troubling,

unexplained birth-related trends, it does not make sense to blindly

employ a technology that is not reliably safe for unborn babies.

Caroline Rodgers

Editor's Note: Read more about ultrasound on our Web site:

Ultrasound: Weighing the Propaganda Against the Facts - by Beverley

Lawrence Beech

Ultrasound: More Harm than Good? - by Marsden Wagner Search more about

ultrasound.

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