Chronic hypertension is the most likely diagnosis. Hypertension prior to the 20th week of gestation is most consistent with previously undiagnosed chronic hypertension, which may go undetected in healthy women because of a minimal need for medical evaluation prior to pregnancy. As in nonpregnant patients, chronic hypertension may be primary (formerly known as essential) or secondary. This patient presents at the 12th week of gestation with persistently elevated blood pressures since her pregnancy was discovered, suggesting that her hypertension predated her pregnancy, and is likely primary because she has no other clinical features or laboratory study results to suggest a different cause. The 2013 American College of Obstetricians and Gynecologists (ACOG) guidelines recommend treating persistent blood pressure elevations of >160/105 mm Hg in women with chronic hypertension, with a goal blood pressure with medical therapy in these patients being 120-160/80-105 mm Hg.

The diagnosis of gestational hypertension requires consistent hypertension after the 20th week of gestation without preexisting hypertension or features of preeclampsia and must resolve within 12 weeks of delivery. Because this patient is persistently hypertensive early in her pregnancy, gestational hypertension is not likely.

Normal physiologic changes associated with pregnancy include increased cardiac output and decreased systemic vascular resistance and blood pressure. Blood pressure elevations to the level seen in this patient are not normally seen in pregnancy, when blood pressures are usually much lower.

Preeclampsia requires the combination of new-onset hypertension after 20 weeks of pregnancy and end-organ damage such as proteinuria, kidney dysfunction, thrombocytopenia, abnormal liver chemistry tests, pulmonary edema, and cerebral or visual symptoms.