A 38-year-old woman in her 1st pregnancy at 16 weeks gestation is very anxious about the possibility of chromosomal abnormalities in her baby. What is the single best test to give a definitive diagnosis?
A. Amniocentasis
B. Chorionic villous sampling
C. Maternal alpha fetoprotein
D. Nuchal fold thickness
E. Parental karyotype
Ans. The key is A. Amniocentasis. [Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, and also for sex determination, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amniotic sac surrounding a developing fetus, and then the fetal DNA is examined for genetic abnormalities. The most common reason to have an “amnio” is to determine whether a baby has certain genetic disorders or a chromosomal abnormality, such as Down syndrome. Amniocentesis is performed when a woman is between 14 and 16 weeks gestation. Chorionic villous sampling is usually done at 10 to 13 weeks of gestation