Cell-free fetal
DNA has received significant attention for the purposes of prenatal genetic testing in the past decade. Fetal
DNA testing is a new method and promising for many applications such as
aneuploidy screening, prenatal diagnosis, prediction of
preeclampsia and more. A 37-year-old primigravida, with a pregnancy conceived by intracytoplasmic sperm injection (ICSI), was offered non-invasive prenatal testing (
NIPT) due to advanced maternal age.
NIPT performed at 23 weeks' gestation reported a diagnosis of
monosomy X. She was offered an amniocentesis, which revealed a euploid fetus with no
sex chromosome abnormalities. Even with single nucleotide polymorphism-based
NIPT, positive predictive value for detection of
sex chromosome abnormalities is around 50%. Positive results of
NIPT should be heeded with caution and an invasive diagnostic procedure should be performed, especially for rare
chromosomal abnormalities and
sex chromosome abnormalities where
NIPT performs subpar compared to its performance for detection of
trisomy 21.