HealthPartners - Your guide to pregnancy

CARRIER DISORDERS Carrier disorders are caused by a tiny change (an abnormal gene) in a single chromosome. For a baby to have most carrier disorders, both parents must be carriers (have the same abnormal gene) for the disease. Carrier disorders can run in families, races, or ethnic groups. Blood or saliva tests can determine if you or your partner have genes for a number of carrier disorders.

With expanded carrier screening, a single sample is used to screen for different disorders. Companies that offer expanded carrier screening create their own lists of disorders they test for, called screening panels . For more information about expanded carrier screening, ask your health care provider or genetic counselor.

ACOG NOW RECOMMENDS THAT ALL PREGNANT WOMEN BE OFFERED THE FOLLOWING 3 SCREENING TESTS:

A simple blood test that can show if you are a carrier of the CF gene. If both parents test positive as CF carriers, chorionic villus sampling (CVS) or amniocentesis testing can be done to see if the baby will be affected. CF is a life-threatening genetic disease that affects breathing and digestion. A simple blood test that can show if you are a carrier of the SMA gene. Similar to cystic fibrosis testing (above), if both parents test positive, CVS or amniocentesis testing can be done. SMA causes weakness in muscles that eventually makes it hard to sit, walk, or stand. It also affects the muscles used to breathe and swallow. A simple blood test for inherited blood disorders called hemoglobinopathies, a group of blood disorders and diseases that affect red blood cells, including sickle cell disease and thalassemia.

CYSTIC FIBROSIS (CF) CARRIER TEST

SPINAL MUSCULAR ATROPHY (SMA) TEST

HEMOGLOBINOPATHIES

SCREENING FOR NEURAL TUBE DEFECTS

FRAGILE X SYNDROME Fragile X syndrome is a carrier disorder that can cause a range of developmental problems in babies. These include learning disabilities or behavioral disabilities, such as autism and attention deficit hyperactivity disorder, that can cause certain intellectual challenges. Fragile X is the most common form of inherited learning disability and is the No. 1 cause of autism worldwide. Fragile X carrier screening is recommended for people with a family history of fragile X-related disorders or an intellectual disability that suggests fragile X syndrome. NEURAL TUBE DEFECTS Neural tube defects are serious birth defects of the brain, spine, and spinal cord. They are caused by a combination of genetic and environmental factors. The 2 most common neural tube defects are: • Anencephaly – Babies born with this condition have an underdeveloped head and brain. • Spina bifida – Babies with this condition have an opening or gap in their backbone.

An alpha-fetoprotein test (AFP) is a blood test that screens for the risk of a neural tube defect. It may be used by itself or as part of the quad-screen test done at 15-18 weeks. Like all prenatal tests, a normal AFP result does not guarantee that your baby will not have this defect. About 1 in 5 babies born with a neural tube defect will have normal AFP levels. Abnormal results will require additional blood tests, ultrasound, or amniocentesis to confirm the results.

NEED TO KNOW

Only 1 or 2 babies in every 1,000 live births will have a neural tube defect. Parents of another child with this abnormality have the highest risk of it happening again.

12 Your Guide to A Healthy Pregnancy