Which of the following is NOT a symptom of severe preeclampsia?

Severe preeclampsia is characterized by a specific set of symptoms and diagnostic criteria. Among those criteria, a diastolic blood pressure of 90 mmHg is not considered severe on its own. Severe preeclampsia typically involves diastolic blood pressures of 110 mmHg or higher, which reflects a more critical condition that requires urgent medical attention.

Oliguria, defined as urine output of less than 400 mL in 24 hours, is indeed a symptom of severe preeclampsia, as it indicates compromised kidney function. Epigastric pain or heartburn can also occur in situations of severe preeclampsia, often due to liver involvement or hypertension itself. Similarly, retinal arterial spasms are pertinent symptoms related to the changes in vascular health and can manifest due to hypertension and other complications involved in severe preeclampsia.

Thus, while the other options reflect common symptoms or related complications of severe preeclampsia, a diastolic blood pressure of 90 mmHg does not meet the threshold necessary to indicate severe management or severity of the condition.