A nurse in a provider's office is caring for a client who is at 34 weeks of gestation and at risk for placental abruption. The nurse should recognize that which of the following is the most common risk factor for abruption?

Choice A reason: Hypoglycemia is a low blood sugar level that can affect newborns, especially those who are premature, small for gestational age, or have diabetic mothers. However, hypoglycemia does not explain the high FHR, the low Apgar scores, or the pale and tachypneic appearance of the newborn.

Choice B reason: Phrenic nerve injury is a rare complication of cesarean section that can cause diaphragmatic paralysis and respiratory distress in the newborn. However, phrenic nerve injury usually affects only one side of the chest, and does not cause high FHR, low Apgar scores, or pallor.

Choice C reason: Sepsis is a serious infection that can affect newborns, especially those who are exposed to prolonged rupture of membranes, as in this case. Sepsis can cause high FHR, low Apgar scores, pale and tachypneic appearance, and other signs of shock and organ failure.

Choice D reason: Meconium aspiration syndrome is a condition where the newborn inhales meconium-stained amniotic fluid into the lungs, causing respiratory distress. However, meconium aspiration syndrome usually occurs in term or post-term infants, and is associated with low FHR, not high FHR. Meconium aspiration syndrome also causes cyanosis, not pallor.

Choice A reason: Physiological jaundice is not the correct answer, as it is a normal and benign condition that occurs in about 60% of term newborns, and usually appears after the first 24 hours of life. Physiological jaundice is caused by the breakdown of fetal hemoglobin and the immature liver function, and resolves within a few days.

Choice B reason: Maternal cocaine abuse is not the correct answer, as it is a maternal risk factor that can cause various complications in the newborn, such as low birth weight, prematurity, intrauterine growth restriction, or congenital anomalies. Maternal cocaine abuse does not cause jaundice in the newborn, unless it leads to hepatic or renal dysfunction.

Choice C reason: Maternal/newborn blood group incompatibility is the correct answer, as it is a maternal-fetal condition that can cause hemolytic disease of the newborn, which is a severe form of jaundice that can appear within the first 24 hours of life. Maternal/newborn blood group incompatibility occurs when the mother's blood type is Rh negative and the newborn's blood type is Rh positive, or when the mother's blood type is O and the newborn's blood type is A or B. The maternal antibodies cross the placenta and attack the newborn's red blood cells, causing hemolysis, anemia, and hyperbilirubinemia.

Choice D reason: Absence of vitamin K is not the correct answer, as it is a nutritional deficiency that can cause hemorrhagic disease of the newborn, which is a bleeding disorder that can occur within the first week of life. Absence of vitamin K is due to the lack of intestinal flora and the low vitamin K content in breast milk, and can cause bleeding in the skin, mucous membranes, or internal organs. Absence of vitamin K does not cause jaundice in the newborn, unless it leads to hepatic or biliary dysfunction.