How do prenatal testing and postnatal testing differ?

• A. Prenatal testing aims to detect fetal anomalies before birth; postnatal testing confirms diagnosis after birth
• B. Prenatal testing is for environmental exposures
• C. Postnatal testing cannot detect genetic conditions
• D. Prenatal testing is more accurate for all conditions

Answer: (A)

The main idea tested is the difference in timing and purpose between prenatal and postnatal genetic testing. Prenatal testing is done to detect fetal abnormalities before birth, helping with pregnancy management and decisions. Postnatal testing is performed after birth to confirm or refine a diagnosis when a baby or child shows signs or has a family history of a genetic condition. In practice, prenatal testing can include screening methods that assess risk (like ultrasound findings or maternal serum screens) and invasive diagnostic tests that analyze fetal DNA (such as amniocentesis or chorionic villus sampling). Postnatal testing uses similar laboratory tools to diagnose conditions in a newborn or child after birth, often based on phenotype and family history.

This is the best choice because it accurately captures the key difference: before birth versus after birth, with the corresponding aims of detection versus confirmation. The other options don’t fit: environmental exposures are not the primary focus of genetic testing, postnatal testing can indeed detect genetic conditions, and prenatal testing is not universally more accurate for all conditions.