Every new child is full of surprises. You expect him to look and act like other members of the family, but you never know exactly how his genes will fall together. He could have mom's eyes and dad's hair, but it could just as easily be the other way around.
Unfortunately, his genes could also carry the blueprint for a serious disease. If you're pregnant or thinking about starting a family, genetic diseases are a very real concern. Some pregnancies are especially risky, often because of a mother's age, her health, or a family history of genetic abnormalities. If your doctor sees any red flags, he or she may refer you to a genetic counselor. The counselor can explain potential risks to your baby, recommend tests, interpret test results, and help you consider your options.
While most couples don't seek genetic counseling, it might be right for you. Here are some common reasons why couples are referred to a genetic counselor:
- The mother has had two or more miscarriages, stillbirths, or children who died in infancy. These tragedies might just be a coincidence, but there's also a chance that the babies are inheriting genes that threaten their survival. If you have a history of multiple miscarriages, your doctor may order a blood test to take a closer look at your genetic makeup. After you've conceived, you may want an amniocentesis test to see if your baby has a genetic disease. This decision is complicated by the fact that amniocentesis itself can, in rare cases, cause miscarriages. A genetic counselor can help you decide if the value of the information is worth the risk.
- The mother is over 35 years old. Women of this age are more likely to have a baby with Down syndrome, a condition caused by an extra chromosome. The risk increases steadily with the mother's age. A genetic counselor can calculate the risk in your situation and discuss the screening tests that are used to detect Down syndrome, including amniocentesis, which examines a sample of amniotic fluid,and chorionic villus sampling (CVS), which examines the developing placenta. There are newer tests that can help detect this even earlier, such as nuchal translucency testing, which measures the fluid at the back of the baby's neck, and early markers that can be tested in the mom's blood.
- The mother or father has a family history of genetic disorders. Common examples of inherited genetic disorders include cystic fibrosis, sickle cell anemia, and Tay-Sachs disease. In most cases, these diseases can affect your baby only if both you and your partner carry genes for the disease. If you have a family history of such diseases, a genetic counselor may recommend blood tests to see if you or your partner are "carriers," which means you could pass on the genes. If neither of you are carriers for a particular disease, your child is likely to be safe. If one of you is a carrier, your child won't get the disease, but he could be a carrier himself. (A few conditions, such as Huntington's disease, require only one faulty gene, so your child could get the disease even if only one parent is a carrier.)
- If both of you are carriers, there's generally a one in four chance that your child will have the disease and a 50 percent chance that the child will be a carrier who exhibits no symptoms. (The odds will be greater for diseases like Huntington's -- about 50 percent higher if one parent has a gene for it, and 75 percent if both parents do.) After the baby is conceived, amniocentesis, CVS, or a similar screening test can usually determine whether the baby actually has the disease.
- The parents have an ethnic background that puts them at high risk for genetic diseases. Some inherited diseases are especially common in certain ethnic groups. For example, sickle cell anemia mainly affects people of African ancestry, Tay-Sachs disease is especially common among Jewish people of Eastern or Central European descent, and beta thalassemia generally strikes people with Italian, Greek, or Middle Eastern heritage. Alpha thalassemia is common in Southeast Asian populations. Again, a simple blood test can determine whether you or your partner are carriers for these diseases, and amniocentesis or another screening test can usually determine if your baby has the disease.
- Today, as people of different races and nationalities marry, it is harder to be sure what you are at risk for based on what you look like or what country you come from. For example, a woman of Chinese and Brazilian heritage may not know if she has a Jewish ancestor. If the father of her baby is also Jewish, their child may be at risk for a rare disease common among people of Jewish ancestry.
- An ultrasound or a non-invasive genetic screening involving blood tests and ultrasound shows abnormal results. If a screening test looks abnormal, a genetic counselor can help you interpret the results and recommend further tests to confirm or rule out a genetic disease.
- The parents have other children with birth defects or genetic disorders. A genetic counselor can help determine the risks to future children.
- The mother has been exposed to radiation or chemicals -- including alcohol and illegal drugs -- that could cause genetic defects. A genetic counselor can determine whether the baby is likely to have defects and suggest options for testing.
- The parents have any questions about genes and birth defects. The American Congress of Obstetricians and Gynecologists now recommends that non-invasive and diagnostic genetic testing be offered to all women, regardless of age; doctors may recommend an amnio or CVS to you if the results of a non-invasive screening suggest a higher-than-normal risk.
- Even if your doctor doesn't specifically recommend a visit with a genetic counselor, you can always make an appointment yourself. Just ask your doctor or the local chapter of the March of Dimes for a referral. The visit should give you a little extra peace of mind -- a valuable commodity with a baby on the way.
March of Dimes. Genetic Counseling. http://www.marchofdimes.com/pnhec/4439_15008.asp
Mayo Clinic. Reasons to seek genetic counseling. http://www.mayoclinic.org/genetic-counseling-sct/reasons.html
American Pregnancy Association. Genetic counseling. http://www.americanpregnancy.org/gettingpregnant/geneticcounseling.html
National Institute of Child Health and Human Development. Facts about Down syndrome. http://www.nichd.nih.gov/publications/pubs/downsyndrome/down.htm
USCF Children's Hospital. Other Genetic Diseases: Prenatal Diagnosis. http://www.ucsfhealth.org/childrens/medical_services/preg/ prenatal/conditions/other/diagnosis.html