The nurse preceptor is teaching about the physiology of the fetal heart rate (FHR) pattern.

Which statement by the student indicates a lack of understanding?

Choice A rationale
A non-stress test (NST) is a common test used to evaluate fetal well-being, especially in cases of decreased fetal movement. It measures the fetal heart rate in response to its movements. A reactive NST, where the fetal heart rate increases with movement, indicates good oxygenation and neurological function.
Choice B rationale
A contraction stress test (CST) evaluates the fetal heart rate response to uterine contractions, which can be induced by oxytocin or nipple stimulation. It is typically used to assess placental function and fetal tolerance to labor, not for initial assessment of decreased fetal movement.
Choice C rationale
A biophysical profile (BPP) combines an NST with ultrasound to assess fetal breathing, movement, tone, and amniotic fluid volume. While comprehensive, it is more time-consuming and usually reserved for further evaluation if the NST is non-reactive.
Choice D rationale
An ultrasound can assess fetal growth, amniotic fluid volume, and anatomical structures. However, it does not provide real-time information on fetal heart rate reactivity, making it less suitable for immediate assessment of decreased fetal movement.

Choice A rationale
Amniocentesis is a diagnostic test that involves extracting a small amount of amniotic fluid from the uterus to test for chromosomal abnormalities and genetic disorders. It is typically performed between 15 and 20 weeks of pregnancy. The fluid contains fetal cells and various chemicals produced by the baby, which can be analyzed to detect conditions such as Down syndrome, trisomy 18, and neural tube defects. This test is highly accurate and is often recommended when screening tests like the MSAFP indicate a potential issue.
Choice B rationale
A Nonstress Test (NST) is a non-invasive test that measures the fetal heart rate in response to its movements. It is used to assess fetal well-being, particularly in the third trimester, but it does not provide information about chromosomal abnormalities. The NST is typically used to monitor high-risk pregnancies and to ensure that the fetus is receiving enough oxygen.
Choice C rationale
A Biophysical Profile (BPP) combines an ultrasound with a Nonstress Test to evaluate the fetus’s health. It assesses fetal breathing movements, body movements, muscle tone, amniotic fluid volume, and heart rate reactivity. While it provides a comprehensive assessment of fetal well-being, it does not specifically diagnose chromosomal abnormalities. The BPP is often used in the third trimester to monitor high-risk pregnancies.
Choice D rationale
Chorionic Villus Sampling (CVS) is another diagnostic test that can detect chromosomal abnormalities and genetic disorders. It involves taking a small sample of placental tissue (chorionic villi) for analysis. CVS is typically performed between 10 and 13 weeks of pregnancy, earlier than amniocentesis. While it provides similar diagnostic information, it is not the test of choice following an abnormal MSAFP result, which is usually conducted later in pregnancy.