A nurse is caring for a client who is at 22 weeks of gestation and has been unable to control her gestational diabetes mellitus with diet and exercise. The nurse should anticipate a prescription from the provider for which of the following medications for the client?

Choice A reason: Painless red vaginal bleeding is the most characteristic finding of placenta previa, which is a condition where the placenta covers the cervical opening and can cause bleeding in the third trimester. Painless red vaginal bleeding occurs because the placenta is detached from the lower uterine segment as the cervix dilates or effaces, and the blood vessels are torn. The bleeding can be mild or severe, and it can recur or persist until delivery.

Choice B reason: Intermittent abdominal pain following passage of bloody mucus is not a finding that supports placenta previa, but rather a finding that suggests normal labor or preterm labor. Intermittent abdominal pain is caused by uterine contractions, which can be regular or irregular, and can increase in frequency, duration, and intensity. Bloody mucus is the mucus plug that is expelled from the cervix as it dilates or effaces, and it can be tinged with blood or streaked with blood.

Choice C reason: Increasing abdominal pain with a nonrelaxed uterus is not a finding that supports placenta previa, but rather a finding that indicates abruptio placentae, which is a premature separation of the placenta from the uterine wall. Increasing abdominal pain is caused by the bleeding and the hematoma formation behind the placenta, which can compress the uterine muscle and the nerve endings. Nonrelaxed uterus is a sign of uterine hypertonicity, which can reduce the blood flow and the oxygen delivery to the fetus.

Choice D reason: Abdominal pain with scant red vaginal bleeding is not a finding that supports placenta previa, but rather a finding that suggests ectopic pregnancy, which is a condition where the fertilized ovum implants outside the uterine cavity, usually in the fallopian tube. Abdominal pain is caused by the rupture of the tube and the bleeding into the peritoneal cavity, which can irritate the diaphragm and the abdominal wall. Scant red vaginal bleeding is a sign of implantation bleeding, which can occur when the fertilized ovum attaches to the tube wall.

Choice A reason: This statement is correct, as the ultrasound can help diagnose placenta previa, which is a condition where the placenta covers the cervical opening and can cause painless, bright red bleeding in the third trimester. Placenta previa is a serious complication that can affect the delivery and the fetal oxygenation.

Choice B reason: This statement is incorrect, as the biparietal diameter is a measurement of the fetal head that is used to estimate the gestational age and the fetal growth. The biparietal diameter is not related to the cause or the severity of the bleeding.

Choice C reason: This statement is incorrect, as the fetal lung maturity is an assessment of the surfactant level in the amniotic fluid that is used to predict the risk of respiratory distress syndrome in preterm infants. The fetal lung maturity is not related to the cause or the severity of the bleeding.

Choice D reason: This statement is incorrect, as the viability of the fetus is an evaluation of the fetal heart rate, movement, and tone that is used to determine the fetal well-being and distress. The viability of the fetus is not related to the cause or the severity of the bleeding, although it can be affected by it.