Fetal choroid plexus cysts greater than one centimeter are likely to establish a chromosomal abnormality in the fetus if the pregnancy is to be terminated. Choroid plexus cysts are pseudocysts filled with cerebrospinal fluid in the choroid plexus and are more common in the fetus. Most choroid plexus cysts resolve gradually over time. A choroid plexus cyst may be detected on ultrasound, usually after 10 weeks of pregnancy, and will gradually disappear after 26 weeks of pregnancy. If this cyst is larger than one centimeter in diameter, or if it does not tend to get smaller, this is the time for further tests to be done to detect the presence of the cyst, such as amniocentesis and umbilical cordocentesis. If it is determined that the fetus has a chromosomal abnormality by amniocentesis or umbilical cord blood sampling, the pregnancy will need to be terminated in a timely manner, i.e., induced abortion, depending on the doctor’s instructions.