Choroid Plexus Cyst in Baby: Understanding Causes & Outlook

Question
My sister-in-law has 2 children and she is currently 19-20 weeks pregnant.  Her due date is 9/20/06.  She went for an ultrasound last Friday and they found a plexus cyst on the baby's brain.  She is going to a specialist tomorrow but I was wondering what can be done and how common is it for her to have a normal baby.  We are very worried.

Answer
Don't worry. A choroid Plexus cyst is caused by a collection of cerebrospinal fluid within the folds of the choroid plexus. It occurs in 0.18-3.6%  of sonograms during the 2nd trimester. The cyst usually disappears in the 3rd trimester. The cysts that remain are usually benign and asymptomatic.  The finding is a very common finding on sonogram examinations.  There has been some evidence that there may be chromosomal abnormalities when we see the choroid plexus cysts, but unless there are other abnormalies seen on sonogram, we do not usually investigate further. I would not worry at all about the cyst, since in the vast majority  of cases, the cyst disappears before the delivery of the baby.