A nurse is performing an abdominal ultrasound for a client who is at 28 weeks of gestation.

The nurse should instruct the client to do which of the following before the procedure?

A low level of AFP (<0.5 MoM) in a pregnant woman can indicate that the fetus has a chromosomal abnormality, such as Down syndrome or Edwards syndrome.

This is because these conditions affect the development of the fetal liver, which produces AFP.

Choice A is wrong because neural tube defects, such as spina bifida, are associated with high levels of AFP (>2.5 MoM) in the maternal blood.

This is because AFP can leak from the open spinal canal of the fetus into the amniotic fluid and then into the maternal blood.

Choice C is wrong because maternal weight-related factors do not affect the level of AFP in the maternal blood.

However, they can affect the interpretation of the AFP test results, as the test needs to be adjusted for maternal weight, age, ethnicity, and gestational age.

Choice D is wrong because fetal demise (death) can also cause high levels of AFP in the maternal blood, as the AFP from the dead fetus can leak into the amniotic fluid and then into the maternal blood.

Normal ranges of AFP in pregnant women vary depending on the gestational age and the method of measurement.

Generally, normal levels of AFP are below 10 ng/ml in nonpregnant adults and below 2.5 MoM in pregnant women.

This test can detect genetic disorders.

Chorionic villus sampling (CVS) is a prenatal test that involves taking a sample of tissue from the placenta to test for chromosomal abnormalities and certain other genetic problems.

The placenta is a structure in the uterus that provides blood and nutrients from the mother to the fetus.

Choice A is wrong because CVS does not provide information on neural tube defects, such as spina bifida.

For this reason, women who undergo CVS also need a follow-up blood test between 16 to 18 weeks of their pregnancy to screen for neural tube defects.

Choice C is wrong because CVS can detect chromosomal abnormalities, but not all chromosomal abnormalities are genetic disorders.

For example, Down syndrome is a chromosomal abnormality caused by an extra copy of chromosome 21, but it is not inherited from the parents.

Choice D is wrong because CVS cannot detect Rh sensitization, which is a condition where the mother’s immune system produces antibodies against the fetus’s blood type.

Rh sensitization can be detected by a blood test that measures the level of antibodies in the mother’s blood.