HYPERTENSION IN PREGNANCY

Systolic and diastolic BP both decline early in the first trimester, reaching a nadir
by 24–28 weeks; then they gradually rise toward term but never return quite to
prepregnancy baseline.

Diastolic   falls   more    than    systolic,   as  much    as  15  mm  Hg. 

Arterial    BP  is  never   normally    elevated    in  pregnancy.