The nurse discovers a loop of the umbilical cord protruding through the vagina when preparing to perform a vaginal examination. The priority intervention is to:

A. Internal fetal monitoring. Internal fetal monitoring is contraindicated when placenta previa is suspected because it involves inserting a catheter or electrode into the uterus, which can increase the risk of hemorrhage if the placenta is covering the cervix.

B. Amniocentesis for fetal lung maturity. While fetal lung maturity assessment may be relevant if early delivery is being considered, it is not an immediate diagnostic procedure for evaluating the cause of vaginal bleeding. The priority is to determine placenta location and rule out placenta previa.

C. Contraction stress test. A contraction stress test evaluates fetal response to contractions but is not the appropriate initial diagnostic test in a patient with vaginal bleeding. Stimulating contractions could worsen bleeding if placenta previa or another placental abnormality is present.

D. Ultrasound for placenta location. The first-line diagnostic test for painless, bright red vaginal bleeding in the third trimester is an ultrasound. It helps determine whether the bleeding is due to placenta previa, a condition where the placenta partially or completely covers the cervix, which requires careful management to prevent complications.

A. "An ectopic pregnancy does not need major treatment and can be delivered vaginally." This statement is incorrect. An ectopic pregnancy involves the fertilized ovum implanting outside the uterus, most commonly in a fallopian tube, which poses serious risks to the mother. The pregnancy cannot be carried to term, and it requires prompt medical intervention, such as medication or surgery, to prevent life-threatening complications.
B. "An ectopic pregnancy involves a fertilized ovum outside the uterus that cannot be transferred to the uterus." This is an accurate explanation of an ectopic pregnancy. The fertilized egg implants outside the uterus, most commonly in the fallopian tubes, and cannot develop into a viable pregnancy. The condition requires immediate treatment to prevent tube rupture and internal bleeding.
C. "An ectopic pregnancy involves a cancerous fertilized ovum in either fallopian tube." This is incorrect. An ectopic pregnancy is not cancerous. It refers to a pregnancy where the fertilized ovum implants in an abnormal location outside the uterus, most commonly the fallopian tubes, not involving cancerous growth.
D. "An ectopic pregnancy involves a fertilized ovum in the vagina." This statement is incorrect. An ectopic pregnancy occurs when the fertilized ovum implants outside the uterus, but it does not implant in the vagina. The condition most commonly involves the fallopian tubes but can also occur in other locations such as the cervix, ovary, or abdominal cavity.