Which procedure is used to analyze fetal chromosomes in early pregnancy, typically between 15-18 weeks?

• A. Amniocentesis
• B. Chorionic villus sampling
• C. Cordocentesis
• D. Embryoscopy

Answer: (A)

Obtaining fetal cells for chromosomal analysis in mid-pregnancy is done most commonly with amniocentesis. Fetal cells shed into the amniotic fluid can be collected and cultured to produce a karyotype, revealing chromosome number and structure. The typical safe window for this test is around 15–18 weeks, when enough fluid can be sampled with relatively low risk to the fetus. Chorionic villus sampling uses placental tissue and is performed earlier, usually before 14 weeks, so it's not the described timeframe. Cordocentesis involves sampling fetal blood and is used in different clinical scenarios and carries its own risks, often later in pregnancy. Embryoscopy is for direct visualization of the embryo, not chromosome analysis. Thus amniocentesis is the procedure that matches the scenario.