Final answer:
The highest importance nursing intervention at this time is to notify the primary healthcare provider regarding the mother's signs of severe preeclampsia.
Step-by-step explanation:
The nursing intervention of highest importance at this time for a 36-year-old primigravida receiving treatment for preeclampsia at 29 weeks' gestation is d. Notifying the primary healthcare provider regarding the epigastric pain, headache, and blurred vision.
Epigastric pain, headache, and blurred vision are signs and symptoms of severe preeclampsia, a potentially life-threatening condition. It is crucial to promptly notify the primary healthcare provider so that appropriate interventions can be initiated to prevent complications for both the mother and the fetus.
Assessing fetal heart rate, promoting adequate urine output, and monitoring respiratory status are important interventions, but they are not as high of a priority as notifying the primary healthcare provider when signs of severe preeclampsia are present.