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 mosquitoes do not transmit HIV. HIV is a virus that infects human cells and cannot survive in insects. Mosquitoes do not inject blood from one person to another when they bite, but only saliva that contains anticoagulants and enzymes.

Choice B Reason: This is incorrect because accidental puncture wounds are not a common mode of HIV transmission. HIV can be transmitted through exposure to infected blood or body fluids, such as through needle sharing, blood transfusion, or occupational injury. However, these cases are rare and can be prevented by using sterile equipment, screening blood products, and following universal precautions.

Choice C Reason: This is incorrect because casual contact is not a mode of HIV transmission. HIV is not an airborne virus and cannot be spread by coughing, sneezing, or breathing. HIV cannot be transmitted by hugging, kissing, or sharing utensils.

Choice D Reason: This is correct because direct contact with infected body fluids is the most common mode of HIV transmission. HIV can be transmitted through unprotected vaginal, anal, or oral sex with an infected person, as these activities can involve contact with infected blood, semen, vaginal fluid, or pre-ejaculate. HIV can also be transmitted through sharing needles or syringes with an infected person, or from mother to child during pregnancy, childbirth, or breastfeeding.

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.