Birth Defects

If you're like most expecting 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 heart defects, which affect one in 100 babies in the United States. Some other common structural defects include rubella (German measles), syphilis, toxoplasmosis, Venezuelan equine encephalitis, parvovirus, and, rarely,

What Causes 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 one 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.

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 birth. The two most common forms of NTDs are:

• Spina bifida, 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.
• Anencephaly, which occurs in three 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 one 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 trimester. Women must make sure that they are receiving enough folic acid before they become pregnant because the neural tube closes during the period about 1 week after the first missed menstrual period - so mothers cannot wait to start folic acid when they first realize they are pregnant. For this reason, it is recommended that women of reproductive age take folic acid throughout their reproductive years.

These are among the most common defects, occurring in as many as one 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

Some cases of cerebral palsy are caused by 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 equipment and Speech therapy and 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 - one in four children with two parents who carry the gene for CF will get the disease; one 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.

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:

• esophageal atresia, or incomplete development of the esophagus
• diaphragmatic hernia, 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
• pyloric stenosis, 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 esophagus (vomiting)
• Hirschsprung's disease, 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
• anal atresia 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
• biliary atresia, in which the bile-carrying ducts in the liver either didn't develop or developed abnormally

The frequencies of these disorders vary, ranging from one in 32,000 births to one 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 these defects.

Down syndrome 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 one in 800 and one 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 one in 350 chance of having a baby with Down syndrome, and a woman who's 45 has a one in 30 chance. 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.

Phenylketonuria (PKU) 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 time she's a year old. About one baby in 10,000 to 25,000 in the United States is born with PKU. This is a genetic disorder; if both parents carry the gene, there's a one in four 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 prevented.

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 one in 2,000 males and one in 4,000 females of all races and ethnic groups.

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 Muscular dystrophy 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.

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.

Infections during pregnancy can cause a variety of birth defects. Some examples are:

• 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.
• Fifth disease can cause a dangerous form of anemia, heart failure, and, in some cases, fetal death,
• Congenital varicella syndrome, which is caused by chicken pox, 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 chicken pox.

Talk to your health care provider about ways you can 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. The list of defects that may be detected through prenatal screening includes:

• 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 should have and discuss any concerns you have about testing.

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 that can screen for many additional disorders of metabolism on a small blood sample is now being adopted by many state newborn screening programs.

The National Institutes of Health recommend that all African-American babies be tested for sickle cell anemia; about 40 states currently do so. Other disorders that your state may test newborns for include:

• 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 a specific birth defect, you may be able to have your baby tested for it as well. 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, there are some common-sense precautions you can take 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, and that they are getting the daily recommended dose of folic acid (which is present in orange juice and green leafy vegetables, or can be taken as a supplement in pill form). One way to ensure that you are getting enough is to start taking prenatal vitamins as soon as you begin trying to conceive. 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), you might want to consult 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 viable 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 have.

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 (make sure you're getting enough folic acid)
• 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.

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