Which prenatal test samples amniotic fluid via a needle inserted into the uterus?

• A. Chorionic villus sampling
• B. Amniocentesis
• C. Percutaneous umbilical blood sampling
• D. Ultrasound

Answer: (B)

Amniocentesis is the procedure that samples amniotic fluid by inserting a needle through the mother's abdomen into the uterus under ultrasound guidance to withdraw a small amount of fluid surrounding the fetus. This fluid contains fetal cells and biochemicals that are analyzed for genetic testing, fetal infections, and lung maturity. It directly targets the amniotic fluid, unlike the other options: chorionic villus sampling collects placental tissue earlier in pregnancy, perinatal umbilical blood sampling draws fetal blood from the umbilical cord, and ultrasound is used for imaging rather than sampling fluid. So, the test that specifically samples amniotic fluid is amniocentesis.