Q&A: My pregnancy genetic screening says I have a half a chromosomal marker for cystic fibrosis.

A chromosomal marker, or a genetic marker, is defined by the Merriam Webster Medical Dictionary as, "a readily recognizable genetic trait, gene, DNA segment, or gene product used for identification purposes especially when closely linked to a trait or to genetic material that is difficult to identify."

Researchers have increased their ability to identify when someone is a carrier of a particular condition (in your case cystic fibrosis or CF) by not only looking at the portion of DNA it is associated with, but also by looking at the segments around it. There can be changes or mutations in the segments that are associated with the cystic fibrosis trait. As researchers learn more, they are discovering more and different markers that may also point to the possibility of a positive result. Marker tests are usually done on people who have a family history of cystic fibrosis. As with any prenatal testing there is always the chance that the "positive" results could in fact be a false negative.

CF is what is known as a recessive disorder, meaning it may be passed on to a child if both parents are carriers of the gene. Your healthcare providers can be more alert to symptoms if your child might be at risk to develop CF if you have had any kind of positive results.

"Cystic fibrosis is the second most common (after sickle cell anemia) life-shortening, childhood-onset inherited disorder in the United States. Each year, approximately 1,000 persons in the United States receive a diagnosis of CF," according to the Centers for Disease Control and Prevention (CDC).

In addition to genetic screening in pregnancy, many states are now doing screening (with a simple blood test) on babies once they are born. Your healthcare providers can be more alert to symptoms if your child might be at risk of developing CF if you have had any kind of positive results. Talking with a geneticist or your doctor will be helpful in interpreting your particular results.