Find out what birth defects are detected by amnio
Down syndrome is caused when an extra chromosome 21 is present. Spina bifida is when there is a hole in the sack that covers the spinal cord. Since the presence of the hole allows spinal fluid to leak into the amniotic fluid around the baby, the spinal fluid can be detected very accurately by amniocentesis.
During an amniocentesis, fetal cells are obtained. With these cells the number of chromosomes and the presence of an extra chromosome (trisomy) can be determined. The test can also detect other types of disorders if the lab is asked to check for a specific inherited disease based on the mother's family history. Sickle cell anemia, for example, can be determined by amniocentesis.
A normal amniocentesis unfortunately does not guarantee a perfect baby. Any other structural defect of the baby that is not caused by a genetic abnormality and does not alter the fluid around the baby cannot be detected by amniocentesis. Three percent of all babies will be born with some structural defect such as cleft lip or clubfoot. Ultrasound can help predict some of these abnormalities, but the detection rate is not 100 percent.