A nurse is explaining the purpose of a Contraction Stress Test (CST) to a pregnant client.

What does the CST aim to assess?

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 is because a nuchal translucency ultrasound measures the amount of fluid behind the baby’s neck in the first trimester of pregnancy, which can indicate the risk of having a chromosomal condition like Down syndrome.

Some possible explanations for the other choices are:

Choice A is wrong because fetal growth and development are not directly related to the nuchal translucency measurement.

Fetal growth and development are assessed by other parameters such as crown-rump length, biparietal diameter, abdominal circumference, etc.

Choice B is wrong because blood flow in the umbilical cord is not measured by the nuchal translucency ultrasound.

Blood flow in the umbilical cord is assessed by Doppler ultrasound, which evaluates the resistance and velocity of blood flow in the umbilical artery and vein.

Choice D is wrong because structural abnormalities in the baby’s organs are not detected by the nuchal translucency ultrasound.

Structural abnormalities in the baby’s organs are diagnosed by a detailed anatomy scan, which is usually performed in the second trimester of pregnancy.

The normal range for nuchal translucency is between 1 mm and 3 mm.

A measurement above 3 mm is considered increased and may indicate a higher risk of chromosomal or genetic conditions.

However, a nuchal translucency ultrasound is a screening test and not a diagnostic test, so it does not confirm or rule out any condition.

It only provides a probability based on statistical calculations.

Therefore, further testing may be recommended if the nuchal translucency measurement is increased or if other risk factors are present.