DISCUSSION
We have derived reference ranges for blood pressure from
12 to 40 weeks gestation in a large population-based
pregnancy cohort and compared these with reference
ranges for women who had a normal pregnancy, without
essential hypertension or preeclampsia, existing or gestational
diabetes who delivered an appropriate-sized infant at
term. We found that normal pregnancies had generally
lower upper reference range limits and narrower reference
ranges throughout pregnancy. We also observed differences
in reference ranges between different subgroups
of women with normal pregnancies based on prepregnancy
BMI, smoking and parity and found that the expected
normal trajectory of blood pressure differed by the blood