Blood pressure of a pregnant women commonly falls from the first trimester of pregnancy to it's lowest value during the second trimester. The maximum drop in BP is usually around systolic BP of 30 and diastolic BP of 15.
BP returns back to pre-pregnant levels by term.
Hypertension in pregnancy occurs when there is an increase of BP more than 140/90 in the 2nd half of pregnancy and is due to increase vascular resistance. Protein excretion in pregnancy should be less than 0.5g/24hr.
Patients who develop pregnancy induced hypertension are at increase risk of developing hypertension later in life.