Karyotype refers to the number and visual appearance of an individual’s chromosomes. A fetal karyotype test may be recommended due to maternal age-related risk or when less invasive prenatal screenings like maternal serum screening show an increased risk for aneuploidy, or chromosomal abnormalities. A karyotype test provides a picture of the baby’s chromosomes, which allows for a close examination of each chromosome to determine if the chromosomes are normal, missing, or if there are extra.
In order to get this picture, a sample of the baby’s cells is necessary. There are two ways to get this sample: chorionic villus sampling (CVS) and amniocentesis.
The most common chromosomal abnormalities screened for during karyotype testing are trisomy 13, trisomy 18, trisomy 21 (Down syndrome), trisomy 23 (Klinefelter syndrome), and Turner syndrome.
Fetal karyotype testing is different from early prenatal screenings. Early prenatal screenings provide insight into the risk or probability of a chromosomal abnormality. The results from fetal karyotype testing via amniocentesis or chorionic villus sampling (CVS) are definitive, providing a clear answer and diagnosis. [38]