Testing & Diagnosis for Trisomy 18 and 13 in Children


Chromosomal abnormalities such as trisomy 18 and 13 can be diagnosed before birth by analyzing cells in the amniotic fluid (amniocentesis) or from the placenta.

  • Fetal ultrasound during pregnancy can also give information about the possibility of trisomy 18 or 13, but ultrasound is not 100 percent accurate because some babies with trisomy 18 and 13 may look the same on ultrasound as those without the syndrome.
  • A chromosome analysis, whether performed on a blood sample, cells from the amniotic fluid, or placenta, is over 99.9 percent accurate.

Since trisomy 18 and trisomy 13 each have a unique group of characteristics, a physician may be able to determine simply by physical examination whether a baby has trisomy 18 or 13. To confirm the physical findings, a small blood sample can be taken and the chromosomes can be analyzed to determine the presence of an extra 18 or 13 chromosome.