A pregnant woman undergoes a triple/quadruple screen at 16 to 18 weeks' gestation. What would the nurse suspect if the woman's alpha-fetoprotein (AFP) level is decreased?

Choice A Reason: This is incorrect because sickle-cell anemia is a genetic disorder that affects the shape and function of red blood cells. It does not affect the AFP level, which is a protein produced by the fetus and placenta. Sickle-cell anemia can be detected by other prenatal tests, such as hemoglobin electrophoresis or DNA analysis.

Choice B Reason: This is incorrect because cardiac defects are structural abnormalities of the heart or blood vessels that affect the blood flow and oxygen delivery to the fetus. They may cause an increased AFP level, not a decreased one, as they can lead to fetal distress or edema. Cardiac defects can be detected by other prenatal tests, such as fetal echocardiography or ultrasound.

Choice C Reason: This is correct because Down syndrome is a chromosomal disorder that results from an extra copy of chromosome 21. It causes various physical and mental developmental delays and defects in the fetus. It is associated with a decreased AFP level, as well as decreased levels of human chorionic gonadotropin (hCG) and unconjugated estriol (uE3). Down syndrome can be confirmed by other prenatal tests, such as amniocentesis or chorionic villus sampling (CVS).

Choice D Reason: This is incorrect because respiratory disorders are problems that affect the breathing and gas exchange of the fetus. They may cause an increased AFP level, not a decreased one, as they can lead to fetal distress or edema. Respiratory disorders can be detected by other prenatal tests, such as fetal biophysical profile (BPP) or nonstress test (NST).

Choice A Reason: This is incorrect because sickle-cell anemia is a genetic disorder that affects the shape and function of the red blood cells. It is not related to the AFP level, which is a protein produced by the fetal liver and yolk sac.

Choice B Reason: This is incorrect because cardiac defects are abnormalities in the structure or function of the heart. They are not related to the AFP level, which is a marker of neural tube defects and abdominal wall defects.

Choice C Reason: This is correct because Down syndrome is a chromosomal disorder that results from an extra copy of chromosome 21. It is associated with a decreased AFP level, as well as increased levels of human chorionic gonadotropin (hCG) and unconjugated estriol (uE3).

Choice D Reason: This is incorrect because respiratory disorders are problems that affect the lungs and breathing. They are not related to the AFP level, which reflects the fetal development and integrity.