Because of the miscarriage and fetal damage risks associated with amniocentesis and CVS procedures, many women prefer to first undergo screening so they can find out if the fetus' risk of birth defects is high enough to justify the risks of invasive testing.Since screening tests yield a risk score which represents the chance that the baby has the birth defect, the most common threshold for high-risk is 0.Success rates for retrieving fetal trophoblast cells vary from 40% to 90%.Antibody markers have proven useful to select trophoblast cells for genetic analysis and to demonstrate that the abundance of recoverable trophoblast cells diminishes in abnormal gestations, such as in ectopic pregnancy or anembryonic gestation.
Having this information in advance of the birth means that healthcare staff as well as parents can better prepare themselves for the delivery of a child with a health problem.
Prenatal testing consists of prenatal screening and prenatal diagnosis, which are aspects of prenatal care that focus on detecting problems with the pregnancy as early as possible.
These may be anatomic and physiologic problems with the health of the zygote, embryo, or fetus, either before gestation even starts (as in preimplantation genetic diagnosis) or as early in gestation as practicable.
Additional ultrasounds may be performed if there are any other problems with the pregnancy, or if the pregnancy is post-due. Based on enrichment of fetal cells which circulate in maternal blood.
Since fetal cells hold all the genetic information of the developing fetus, they can be used to perform prenatal diagnosis.