A client who is 15 weeks pregnant comes to the clinic for amniocentesis. Which of the following can amniocentesis determine?

• A. Gestational age
• B. Chromosomal defects
• C. Sex of the fetus
• D. Placental location

Answer: (C)

Amniotic fluid contains fetal cells that can be cultured and analyzed to reveal the fetal karyotype. From this genetic material you can identify the sex chromosomes, so you can determine whether the fetus is XX or XY. That’s why amniocentesis can tell the sex of the fetus, especially by this stage when there are enough fetal cells for accurate testing. By contrast, gestational age and placental location are typically assessed with ultrasound, not amniocentesis. Chromosomal defects can be detected with this test as well, but if you’re choosing the single most direct outcome listed, identifying the sex is a straightforward result of analyzing the fetal chromosomes.