Amniocentesis is typically performed at which gestational age?

Amniocentesis is typically performed at which gestational age?

• A. 8-10 weeks
• B. 12-14 weeks
• C. 16-18 weeks
• D. 20-22 weeks

Answer: (C)

The best time to perform an amniocentesis is in the mid-second trimester, about 16–18 weeks of gestation. At this stage there is enough amniotic fluid and fetal cells shed into the fluid for accurate chromosomal analysis, and ultrasound guidance helps position the needle safely. The risk of procedure-related miscarriage is lower than in earlier pregnancy, and the sample quality is reliable for diagnostic testing. Doing amniocentesis earlier, around 8–10 weeks, isn’t ideal because there’s less fluid and the fetus is smaller, increasing risk. Around 12–14 weeks is more commonly associated with chorionic villus sampling rather than amniocentesis. Later in pregnancy, past about 20 weeks, the procedure becomes more challenging and riskier, and the diagnostic yield for certain tests is affected.

The best time to perform an amniocentesis is in the mid-second trimester, about 16–18 weeks of gestation. At this stage there is enough amniotic fluid and fetal cells shed into the fluid for accurate chromosomal analysis, and ultrasound guidance helps position the needle safely. The risk of procedure-related miscarriage is lower than in earlier pregnancy, and the sample quality is reliable for diagnostic testing.

Doing amniocentesis earlier, around 8–10 weeks, isn’t ideal because there’s less fluid and the fetus is smaller, increasing risk. Around 12–14 weeks is more commonly associated with chorionic villus sampling rather than amniocentesis. Later in pregnancy, past about 20 weeks, the procedure becomes more challenging and riskier, and the diagnostic yield for certain tests is affected.