Invasiveness

Diagnostic prenatal testing can be performed by invasive or non-invasive methods. An invasive adjustment involves probes or all-overs getting amid into the uterus, e.g. amniocentesis, which can be done from about 14 weeks gestation, and usually up to about 20 weeks, and chorionic beard sampling, which can be done beforehand (between 9.5 and 12.5 weeks gestation) but which may be hardly added chancy to the fetus. One abstraction comparing transabdominal chorionic beard sampling with additional trimester amniocentesis begin no significant aberration in the absolute abundance accident amid the two procedures.[1] However, transcervical chorionic beard sampling carries a significantly college risk, compared with a additional trimester amniocentesis, of absolute abundance accident (relative accident 1.40; 95% aplomb breach 1.09 to 1.81) and ad-lib abortion (9.4% risk; about accident 1.50; 95% aplomb breach 1.07 to 2.11).[1]
Non-invasive techniques cover examinations of the woman's abyss through ultrasonography and affectionate serum screens (i.e. Alpha-fetoprotein). Claret tests for baddest trisomies (Down affection in the United States, Down and Edwards syndromes in China) based on audition fetal DNA present in affectionate claret accept become available.[2][3] If an animated accident of chromosomal or abiogenetic aberancy is adumbrated by a non-invasive screening test, a added invasive address may be active to accumulate added information.[4] In the case of neural tube defects, a abundant ultrasound can non-invasively accommodate a absolute diagnosis.