The same thing happened with my fourth child... who is now a totally healthy nine year old.
Choroid Plexus Cysts are sometimes found in babies with Trisomy 18. That is a worst case diagnosis and fairly rare.If
it was Trisomy 18, the baby would most likely have other signs visible on an ultrasound... heart problems, clenched fists, excess amniotic fluid and failure to thrive.
In the vast majority of cases, having CPC means nothing. And if it's nothing, it is truly nothing... no minor disabilities, no minor retardation... nothing.
I was told that doctors are seeing more cases of CPC because the ultrasound machine technology has advanced. Chances are there are plenty of healthy children out there who were never diagnosed with CPC because the ultrasounds back then weren't as sensitive.
Unfortunately, this means that many more parents are being worried needlessly. I asked my midwife, "Next time if the baby has CPC, can you just not tell me?". She said no, that they are obligated to tell you everything they know.
The only way to know for sure is to have an amniocentisis done but that is something I was not willing to do for such a small risk of Trisomy 18. So long as the rest of the ultrasound was normal and the baby is growing appropriately, there is almost certainly nothing to worry about.
Enjoy the rest of your pregnancy!