Like most expectant parents, you probably alternate between
fantasies about a healthy baby and worries that your baby will have
a health problem. Or perhaps you've been told through
that your baby may be born with a birth defect.
Many parents assume that all birth defects are severe or even
fatal, but the fact is that many are treatable, often immediately
after birth - and sometimes even before the baby is born.
It's especially important to know the risk factors involved
and how to prevent birth defects. However, it's also important
to realize that most babies born with congenital defects are born
to two healthy parents.
About Birth Defects
Birth defects are defined as abnormalities of structure,
function, or body metabolism that are present at birth. These
abnormalities lead to mental or physical disabilities or are fatal.
There are more than 4,000 different known birth defects, ranging
from minor to serious, and although many can be treated or cured,
they're the leading cause of death in the first year of
According to the March of Dimes, about 150,000 babies are born
with birth defects each year in the United States. The American
College of Obstetricians and Gynecologists (ACOG) says that 3 out
of every 100 babies born in the United States have some kind of
major birth defect.
Birth defects can be caused by genetic, environmental, or
Structural or metabolic defects
are those that result when a specific body part is missing or
formed incorrectly or when there is an inborn problem in body
chemistry. The most common type of major structural defects are
, which affect 1 in 100 babies in the United States.
Other common structural defects include
and hypospadias, a condition in which the opening of the male
urethra (where urine exits from the penis) is in the wrong
Metabolic defects affect 1 in 3,500 babies and usually involve a
missing or incorrectly formed enzyme (a protein necessary for
processing chemical substances in the body). This type of defect
can be harmful or even fatal, but doesn't usually cause any
visible abnormalities in the child. Metabolic defects include
Tay-Sachs disease, a fatal disease that affects the central nervous
system, and phenylketonuria (PKU), which affects the way the body
Defects caused by congenital infections
result when a mother gets an infection before or during the
pregnancy. Infections that can cause birth defects include
, toxoplasmosis, Venezuelan equine encephalitis, parvovirus, and,
. None of these affect 100% of babies whose mothers are infected
during pregnancy. If the mother is infected during early pregnancy,
rubella carries the highest risk for birth defects (approximately
Other causes of birth defects include alcohol abuse by the
mother and Rh disease, which can occur when the mother's and
baby's Rh factors (the "positive" or
"negative" part of a person's blood type) are
Although a few medications can cause problems, none of the 200
most commonly prescribed drugs are associated with a significant
risk of birth defects.
Most babies with birth defects are born to two parents with no
obvious health problems or risk factors. A woman can do everything
her doctor recommends to deliver a healthy child and still have a
baby with a birth defect.
In fact, according to the March of Dimes, about 60% of birth
defects have unknown causes. The rest are caused by environmental
or genetic factors, or some combination of the two.
play a role in some birth defects. Every cell in the body has
chromosomes containing genes that determine a person's unique
characteristics. One missing or faulty gene can cause a birth
defect; this is significant when you consider that we each have
about 25,000 genes per cell determining everything from the length
of our toes to the color of our eyes.
Where do the faulty genes come from? A child inherits one of
each pair of chromosomes (and one of each pair of the genes they
contain) from each parent. Sometimes, a disease or defect can occur
if only one parent passes along the gene for that disease (even
though the child receives a normal gene from the other parent);
this is called dominant inheritance and includes birth defects such
as achondroplasia (a form of dwarfism) and Marfan syndrome (a
disorder characterized by abnormally long fingers, arms, and
Some birth defects occur only when both parents (who are
healthy) each pass along a faulty gene for the same disease to the
child; this is called recessive inheritance and includes conditions
such as Tay-Sachs disease or cystic fibrosis.
Finally, some boys inherit disorders from genes passed on to
them by their mothers. These defects, which include conditions such
as hemophilia and color-blindness, are called X-linked because the
genes are carried on the X chromosome. Because males have only the
one X chromosome they receive from their mothers (females have two
X chromosomes - one from each parent), a faulty gene on the X
chromosome they receive will cause a problem because they don't
have a normal copy of the gene on the other X chromosome that
The number or structure of chromosomes can also cause birth
defects. An error during the formation of an egg or sperm can cause
a baby to be born with too few or too many chromosomes, or with a
damaged chromosome. Birth defects caused by chromosome problems
include Down syndrome. The risk of this type of birth defect often
increases with the age of the mother.
of birth defects have more to do with the mother's health and
exposure to chemicals or diseases. When a mother has certain
infections, such as rubella, during pregnancy, it can cause birth
defects. Alcohol abuse by the mother causes fetal alcohol syndrome,
and certain medications taken by the mother can cause birth
Multifactorial birth defects
are caused by a combination of genetic and environmental factors
and include neural tube defects and cleft lip and palate.
Although you can take steps to prevent birth defects, a birth
defect can happen even if you or your partner have no history of
birth defects in your families or if you've had healthy
children in the past.
Some Common Birth Defects
Cleft lip and/or palate
occurs when the tissues of the mouth or lip don't form properly
during fetal development. A cleft lip is a long opening between the
upper lip and the nose. A cleft palate is an opening between the
roof of the mouth and the nasal cavity.
In the United States, oral clefting occurs in 1 in 700 to 1,000
births, making it one of the most common major birth defects.
Clefts occur more frequently in children of Asian, Latino, or
Native American descent; it's believed that a variety of
environmental and genetic factors cause clefting, but it's
unknown exactly which ones. Clefting is a birth defect that can be
surgically repaired after birth.
usually isn't detected until weeks to months after birth,
depending on the severity of the condition. The term actually
refers to a group of conditions affecting control of movement and
caused by brain damage. People with cerebral palsy have difficulty
controlling the motions their muscles make - which muscles and how
severely they are impaired varies from person to person.
About 70% of people with cerebral palsy also have other
disabilities, most often mental retardation. Some children may have
trouble walking; others may not be able to swallow or speak.
Cerebral palsy occurs in 2 to 6 of every 1,000 births; about 10,000
children born in the United States each year develop cerebral
In most cases, the cause of cerebral palsy isn't known, but
some causes include:
- rubella (German measles) infection during pregnancy
- Rh disease (a blood problem in the baby that results from a
difference in the mother's and infant's blood types)
- brain damage during the last trimester of pregnancy or around
the time of birth
Cerebral palsy can also have a genetic cause or may be due to
head injuries or meningitis that occur after birth. Therapy to
improve motor skills, surgery, and braces and other types of
can help improve mobility and muscle control.
can help as well.
is a term used to describe a group of structural defects of the
foot and ankle in which the bones, joints, muscles, and blood
vessels are formed incorrectly. These defects range from mild to
severe and may affect one or both feet. Feet affected by this
defect point down, turn in, and usually have a limited range of
This is a relatively common birth defect, affecting about 1 in
735 babies born each year in the United States. Boys are affected
almost twice as often as girls. The cause is unknown, but it can be
treated by applying a cast immediately after birth. This works
about 95% of the time; if it doesn't, surgery and further
casting are usually required.
Congenital hip dislocation
occurs when the round upper end of the thighbone doesn't sit
inside the socket of the pelvis properly. This can happen in one or
both hips. It happens in about 1 or 2 in 1,000 births, more often
in girls, and tends to run in families, although the exact cause is
unknown. Usually it is detected at birth and treated immediately by
placing the baby in a soft sling for 6 to 9 months. If it's not
recognized and treated early, surgery may be necessary.
, which occurs in about 1 in 3,000 to 4,000 births, results when
the baby's thyroid gland (located in the front of the neck) is
absent or underdeveloped at birth. This causes the infant to be
unable to produce adequate amounts of thyroid hormone, which is
important for supporting normal growth and brain development.
Developmental delay and permanent mental retardation can result
if the condition is not recognized and treated (with oral thyroid
hormone) within the first few weeks of life. Because of this, every
state in the United States and most other developed countries
routinely screen all newborns for the condition with a blood test
performed shortly after birth.
Fetal alcohol syndrome (FAS)
is characterized by slowed growth, mental retardation,
abnormalities in facial features, and problems with the central
nervous system. Every year between 2,000 and 12,000 babies in the
United States are born with defects caused by alcohol. FAS cannot
be cured or treated, but can be prevented by avoiding alcohol
intake during pregnancy.
Neural tube defects (NTDs)
occur in the first month of pregnancy when the structure that
develops into the brain and spinal cord is forming. Normally, this
structure folds into a tube by the 29th day after conception. When
the tube doesn't close completely, the baby has an NTD; many
babies with these defects are stillborn or die soon after
The two most common forms of NTDs are:
, which happens when the spinal column doesn't close
completely around the spinal cord. It ranges from mild to severe
and can be associated with loss of bladder and bowel function,
paralysis, and, in some cases, death.
, which occurs in 3 out of 10,000 births, involves the lack of
development of parts of the brain.
NTDs are multifactorial defects, which according to the March of
Dimes occur in about 2,500 babies a year in the United States, or 1
out of every 2,000 live births. Studies have shown that many of
these defects may be prevented when the mother gets enough folic
acid before and during pregnancy, especially during the first
Women must make sure to receive enough folic acid before they
become pregnant because the neural tube closes about 1 week after
the first missed menstrual period - so mothers cannot wait to start
folic acid when they first realize they're pregnant. For this
reason, it is recommended that women take folic acid throughout
their reproductive years.
Defects of the Heart
occur when any of the parts of the heart fail to develop properly.
Atrial and ventricular septal defects
, which are holes in the walls that separate the heart into left
and right sides.
Patent ductus arteriosus
, which is present when the tubular blood channel that allows the
blood to bypass the lungs while the baby is in the womb
doesn't close (as expected) after birth.
Aortic or pulmonary valve stenosis
, which are narrowings of the valves that allow blood to flow
from the heart to the lungs and other parts of the body.
Coarctation of the aorta
, which is a narrowing of the aorta, the major blood vessel
carrying blood from the heart to the rest of the body.
Transposition of the great arteries
, which is the reversal of the connections of the aorta and the
pulmonary artery with the heart.
Hypoplastic left heart system
, which is when the side of the heart that pumps blood to the
body is underdeveloped or nonexistent.
Tetralogy of Fallot
, which is a combination of four heart defects that involves
restriction in the flow of blood to the lungs.
These are among the most common defects, occurring in as many as
1 in 100 births. The specific cause of most heart defects isn't
known, although multiple factors may alter the development of the
heart during the first 8 to 9 weeks of fetal growth.
Exposure to certain medications (such as the antiseizure drug
phenytoin, thalidomide, and chemotherapy drugs) during the first
trimester of pregnancy may play a role in causing heart defects.
Other causes include maternal alcohol abuse, rubella (German
measles) infection, and diabetes during pregnancy.
Defects of the Gastrointestional Tract
Gastrointestinal defects are structural defects that can occur
at any point along the gastrointestinal tract, which is made up of
the esophagus, stomach, small and large intestines, rectum, and
anus. The incomplete or abnormal development of any of these organs
can cause obstructions or blockages that can lead to swallowing
difficulties, vomiting, and problems with bowel movements.
Some of these defects are:
, or incomplete development of the esophagus
, a defect in the layer of muscle separating the chest from the
abdomen that allows some of the abdominal organs to protrude up
into the chest
, a condition in which the muscular wall of the passage carrying
food from the stomach to the small intestine is abnormally thick
and the passage narrow, forcing food back out through the
, in which a section of the large intestine is missing the nerves
that control its contractions, resulting in severe constipation
and sometimes bowel obstruction
gastroschisis and omphalocele
are defects in the abdominal wall allowing the intestine and
other abdominal organs to protrude
involves lack of or incomplete development of the anus, causing
it to be absent or smaller than it should be, often with the
opening in the wrong place
, in which the bile-carrying ducts in the liver either didn't
develop or developed abnormally
The frequencies of these disorders vary, ranging from 1 in
32,000 births to 1 in 10,000 births. Genetics play some role in all
these defects, but it is unclear exactly what role or to what
degree. Early detection and treatment of these defects is
important, as they can lead to serious health problems and even
death if left untreated. Surgery is usually necessary to repair
Genetic Birth Defects
Cystic fibrosis (CF)
is a disease mainly affecting the respiratory and digestive
systems. An inability to carry chloride (one of the chemicals in
table and body salts) from the cells that line organs such as the
lungs and pancreas to their outer surfaces causes the body to
produce a thick, sticky mucus. Children with CF can have trouble
breathing and digesting food; symptoms include chronic respiratory
problems and pneumonia, bulky stools, and poor weight gain.
This defect is genetic - 1 in 4 children with two parents who
carry the gene for CF will get the disease; 1 in 31 people in the
United States carries this gene. It affects approximately 30,000
people in the United States, most of them Caucasians. Treatment
includes therapy to control infections and maintain lung function
and adequate nutrition.
is a group of abnormalities that occur in children who are born
with an extra (third) copy of chromosome number 21 in their cells.
Children with the syndrome have mental retardation and distinctive
facial and other physical features; these problems are often
accompanied by heart defects and other health problems.
The severity of symptoms varies widely from person to person,
with the degree of mental retardation ranging from mild to moderate
to severe. Down syndrome is a relatively common birth defect,
affecting between 1 in 800 and 1 in 1,000 births. The chances of
having a baby with Down syndrome increase dramatically with the age
of the mother; a woman who's 35 has a 1 in 350 chance of having
a baby with Down syndrome, and a woman who's 45 has a 1 in 30
Although some of the health problems caused by Down syndrome
(such as heart defects) may be treated through medication and
surgery, there is no cure.
Fragile X syndrome
is characterized by mental impairment, ranging from learning
disabilities to mental retardation, autistic behaviors, and
attentional problems and hyperactivity. Physical characteristics of
children with Fragile X include a long face, large ears, flat feet,
and extremely flexible joints, especially fingers.
Boys are affected more often than girls, and are more likely to
have mental retardation rather than milder learning impairment.
Both boys and girls are likely to have emotional and behavioral
problems. Recent studies suggest that Fragile X affects about 1 in
2,000 males and 1 in 4,000 females of all races and ethnic
Fragile X is a genetic disorder that's passed on by men who
carry the abnormality to all of their daughters but none of their
sons. Each child of a carrier woman has a 50% chance of inheriting
the genetic abnormality. This means that the Fragile X can be
passed through generations in a family before a child is affected
by the syndrome. There is no cure for Fragile X, although
researchers are exploring ways to prevent it through
is a general term that's used to describe more than 40
different types of muscle diseases, all of which involve
progressive weakness and degeneration of the muscles that control
movement. Heart muscles and some other involuntary muscles are also
affected in some forms of muscular dystrophy, and a few forms
involve other organs as well. The disease is genetic and cannot be
cured. Treatment includes physical and respiratory therapy, the use
of assistive technology, and medications.
is a disease that affects the way the body processes protein; it
can cause mental retardation. A baby born with PKU appears normal,
but if the disease isn't treated, the child will suffer from
developmental delays that are apparent by the first birthday. About
1 baby in 10,000 to 25,000 in the United States is born with
This is a genetic disorder; if both parents carry the gene,
there's a 1 in 4 chance a child will be born with it.
Fortunately, it is usually detected within a few days after birth
by a screening blood test that is routinely performed on infants in
the United States and other developed countries. If the child is
promptly treated with a special diet, retardation can be
Sickle cell disease
is a disorder of the red blood cells in which an abnormal shape of
the cells results in chronic anemia (low blood count), periodic
episodes of pain, and other health problems. The disease is
genetic; if both parents carry the gene, their child has a 1 in 4
chance of having it. In the United States, sickle cell anemia
affects mostly African Americans and some Latinos. The disease
occurs in about 1 in every 500 African-American births and 1 in
every 1,000 to 1,400 Latino-American births.
Treatment for sickle cell disease may include taking antibiotics
to prevent infection, blood transfusions, and bone marrow
transplantation. Parents can be tested to see if they're
carriers of the gene; most U.S. states now routinely perform a
screening blood test for the disease on newborns.
affects the central nervous system, causing blindness, dementia,
paralysis, seizures, and deafness; it's usually fatal within
the first few years of life. Babies with this disease appear normal
when they are born; the symptoms develop during the first few
months of life.
It is genetic and occurs most often in Jews of central or
eastern European descent; when two parents are carriers, a child
has a 1 in 4 chance of having it. Although there isn't any
treatment for this disease, there's a test to help parents
determine if they are carriers of the gene.
Infections That Cause Birth Defects
Infections during pregnancy
can cause a variety of birth defects. Examples include:
- Congenital rubella (the infection posing the highest risk for
fetal damage) syndrome is characterized by vision and/or hearing
loss, heart defects, mental retardation, and cerebral palsy.
- Toxoplasmosis infection of the mother can result in eye
infections that threaten vision, hearing loss, learning
disabilities, enlarged liver or spleen, mental retardation, and
cerebral palsy in the infant.
virus infection of the mother can cause brain damage, cerebral
palsy, vision or hearing impairment, and death of the baby if the
virus is transmitted to the infant before or during the
can cause a dangerous form of anemia, heart failure, and, in some
cases, fetal death.
- Congenital varicella syndrome, which is caused by chickenpox,
can lead to scars, defects of muscle and bone, malformed and
paralyzed limbs, a smaller-than-normal head, blindness, seizures,
and mental retardation. This is an uncommon occurrence in
pregnant women who become infected with chickenpox.
Talk to your health care provider about ways to avoid these
infections while you're pregnant and what you should do if
you're exposed to any of them.
Diagnosing Birth Defects
Routine prenatal screening can do two major things: it can help
determine if the mother has an infection or other condition that is
dangerous to the fetus, and it can help determine if the fetus has
certain birth defects.
Defects that may be detected through prenatal screening
- neural tube defects (spina bifida, anencephaly)
- Down syndrome
- other chromosome abnormalities
- inherited metabolic disorders
- congenital heart defects
- gastrointestinal and kidney malformations
- cleft lip or palate
- certain birth defects of the limbs
- congenital tumors
It's important to remember that screening identifies only
the possibility that a baby has a defect. It's possible to give
birth to a healthy baby after a screening test shows that a defect
may be present. You aren't required to have any prenatal
screening; talk to your doctor about any tests he or she thinks you
Your baby will be tested after birth (with your permission) to
screen for certain birth defects that require treatment soon after
birth. Exactly what your baby will be tested for varies from state
to state (you can ask your health care provider or the hospital
nursery which tests your state performs routinely), although all
states screen for PKU and congenital hypothyroidism.
A new testing technique called tandem mass spectroscopy can
screen for many additional disorders of metabolism on a small blood
sample; it's being used by many states' newborn screening
The National Institutes of Health (NIH) recommends that all
African-American babies be tested for sickle cell disease; about 40
states currently do so.
Other disorders that your state may test newborns for
- cystic fibrosis
- congenital adrenal hyperplasia (an inherited disorder of the
adrenal gland that can cause severe illness in newborns if not
diagnosed and treated within the first few weeks of life)
- hearing loss
If you have a concern about another specific birth defect, you
may be able to have your baby tested for it. Talk to your health
care provider about this before the baby is born.
Can Birth Defects Be Prevented?
Many birth defects can't be prevented; however, you can take
some precautions before and during pregnancy:
Before you get pregnant:
Women who are planning to become pregnant should make sure their
vaccinations are up to date, that they don't have any sexually
transmitted diseases (STDs), and that they get the daily
recommended dose of folic acid. One way to ensure this is to start
taking prenatal vitamins as soon as you begin trying to
It's generally best to avoid unnecessary medications during
pregnancy, so make sure you talk to your doctor about any and all
over-the-counter and prescription medicines you're taking
before you get pregnant; you'll want to stop taking any that
aren't vital to your health. Don't do this without talking
to your doctor, however.
If you or your partner have a history of any kind of birth
defects in your family, if you've already had a child with a
birth defect, or if you are part of a high-risk group (because of
your age, ethnic background, or medical history), consider
consulting a genetic counselor before you get pregnant. More is
being learned about the genes and other factors involved in birth
defects all the time and genetic testing and gene therapy are
becoming increasingly useful aspects of prepregnancy planning and
pregnancy. A genetic counselor can give you advice about prenatal
testing and help you deal with any concerns or fears you might
While you're pregnant:
The best thing that pregnant women can do to increase their
likelihood of having a healthy baby is to make sure they take care
of their bodies during pregnancy by:
- not smoking and avoiding secondhand smoke
- avoiding alcohol
- avoiding all illicit drugs
- eating a healthy diet and taking prenatal vitamins
- getting exercise and plenty of rest
- getting early and regular prenatal care
Talk to your health care provider about other precautions you
can take to protect the health of your baby - don't be afraid
to ask questions if you're concerned.
Linda Nicholson, MS, MC
Date reviewed: October 2007
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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