## **Core Concept**
Antenatal diagnosis involves various techniques to detect fetal abnormalities or diseases during pregnancy. These techniques include ultrasound, amniocentesis, chorionic villus sampling (CVS), and non-invasive prenatal testing (NIPT). The question tests the knowledge of methods used for antenatal diagnosis.

## **Why the Correct Answer is Right**
Ultrasound (A), amniocentesis (B), and chorionic villus sampling (C) are established methods for antenatal diagnosis. Ultrasound is used for imaging the fetus and detecting structural abnormalities. Amniocentesis and CVS are invasive techniques that allow for genetic testing of the fetus.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Ultrasound is a commonly used method for antenatal diagnosis, allowing for the assessment of fetal growth, anatomy, and well-being.
- **Option B:** Amniocentesis is an invasive diagnostic procedure where a sample of amniotic fluid is withdrawn for genetic testing, making it suitable for antenatal diagnosis.
- **Option C:** Chorionic villus sampling (CVS) is another invasive technique used for antenatal diagnosis, where a sample of chorionic villi is taken for genetic testing.

## **Why D is Correct and the Rest are Incorrect as per the Question**
- **Option D:** Maternal serum alpha-fetoprotein (MSAFP) screening is a non-invasive test used for screening, not diagnosis. While it can identify pregnancies at higher risk for certain fetal abnormalities, it does not provide a definitive diagnosis like the other methods mentioned.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while MSAFP screening can identify potential issues, a positive result requires further diagnostic testing (like amniocentesis) for confirmation. This highlights the importance of understanding the difference between screening and diagnostic tests in antenatal care.

## **Correct Answer: D. Maternal serum alpha-fetoprotein (MSAFP) screening**