What are the odds that it is a sign of the chromosomal disorder trisomy 18?
The precise rate of risk is difficult to estimate and is somewhat controversial, but most doctors believe it is well under 1 percent. In other words, a fetus with choroid plexus cysts but an otherwise normal ultrasound has a better than 99 percent chance of not having trisomy 18. A normal alpha fetoprotein (AFP) test further reduces the likelihood of trisomy 18.
