Which of the following abnormalities can be detected by amniocentesis?

The correct option is D Both A and B
In the method of amniocentesis, the amniotic fluid is taken from the sac for testing with the help of a needle under the guidance of ultrasound. It is usually performed between 15 to 16 weeks. It is done to know the chromosomal abnormalities and fetal infections in the womb of mother. It is also used to determine the sex of the child. Down's syndrome (trisomy at 21) is the chromosomal abnormality and neural tube defects are the birth defects of the brain, spine and spinal cord. These can be detected by amniocentesis. So, the correct option is D.