This is where the experts cannot precisely agree. "The vast majority of fetuses with [isolated] CPCs are completely normal, but when CPCs are seen, the chance of Trisomy 18 goes up," says Dr. Doubilet, "This risk is still very small: about 1 in 300." This means that if 300 fetuses have isolated CPCs, only one of them will have Trisomy 18. "While the risk is small, it is higher than the risk of approximately 1 in 3,000 among all pregnant women," points out Dr. Doubilet. Other doctors have reservations: "The problem with this research is that it studied a high-risk population instead of the general population of pregnant women," says Dr. Filly. "I have no instance in 25 years of experience of an isolated CPC indicating Trisomy 18."
Dr. Bronsteen notes, "You need to ask if the person doing the ultrasound exam has the expertise to look for all the abnormalities that are seen with Trisomy 18. In the dozen years we've been tracking it, we did have some babies with an diagnosis of isolated CPC turn out to have Trisomy 18, but in all those cases we did not get a complete look at the baby." His own research indicates that it is very important for the sonographer to view the baby's hands before concluding that the CPC is isolated.
This debate among experts can leave parents bewildered. But even if an isolated CPC does mean an increased risk, that risk is still extremely small. The take-home message? If a CPC is found with no other warning signs, the outcome is virtually always positive.
What Parents Can Do
When a baby is diagnosed with a CPC, there are several things that parents can do. After consultation with their doctor, they will usually undergo a Level II ultrasound. This is a detailed ultrasound exam that is targeted to look for fetal abnormalities. It's important not to rely on the results of a scan performed in a doctor's office or a scan done by someone who is not a trained expert in detecting abnormalities by ultrasound. Only after this kind of intense scan can the diagnosis of an isolated CPC be truly confirmed.
Once other abnormalities besides the CPC have been ruled out, there are two things parents can do: watch and wait, or have an amniocentesis. An amniocentesis is the only way to know for sure before birth that the baby does not have a genetic disease. But even though an amnio can give a sure answer, it carries its own risk. About one in 250 women will miscarry her baby after an amnio, regardless of whether the baby is healthy or not.
The other option is to watch and wait. Generally the doctor will track the progress of the fetus through several follow up ultrasound examinations. Most CPCs will resolve on their own by the sixth month of pregnancy, and a definitive exam of the baby's health can be made after the birth.
While no one can make this decision except the parents and their doctor, many experts suggest that the risk of an amnio is not worth it when the only abnormality the baby has is a CPC. "In our practice, we don't like to do an amnio on somebody whose baby has a very low risk of Trisomy 18 because you wind up losing more normal pregnancies…than you will find Trisomy 18 babies. It doesn't make sense to have a miscarriage of two or three normal babies to find one with Trisomy 18," says Dr. Bronsteen. Your doctor can tell you what his or her recommendation is for your unique situation.
The Angelmans discussed the diagnosis with their doctor and opted to have a Level II ultrasound, which showed no other problems. "It was on the back of our minds the whole pregnancy, and it made it hard not to worry. But our son was born healthy and happy," say Jim and Tina.
After talking with her doctor, Cindy Scoville also decided to have a Level II ultrasound. "At 24 weeks no other abnormalities were found and the sonographer was able to see everything very clearly." says Cindy. "Our little boy is beautiful, healthy and everything we dreamed of. Another happy ending to the worrisome beginning of dealing with a CPC diagnosis during pregnancy."
A CPC diagnosis is scary, no doubt about it. But rest assured that the experts agree that the vast majority of these babies are perfectly healthy, and their CPC is just a normal part of growth and development.