Association between the Change in Blood Pressure during Normotensive Pregnancy and the Development of Hypertension in Later Life

INTRODUCTION: Women who experience maternal complications, including pre-eclampsia, have a higher risk of cardiovascular disease development. Although the mechanism remains unclear, there is a hypothesis that pregnancy would be a stress test for cardiovascular disease. This study aimed to investigate whether changes in blood pressure during pregnancy would be associated with developing hypertension, which is a main risk of cardiovascular disease. METHODS: We conducted a retrospective study by collecting Maternity Health Record Books from 735 middle-aged women. Of these, 520 women were selected based on our criteria. 138 were defined as the hypertensive group according to the criteria of receiving antihypertensive medications or blood pressures of >140/90 mmHg at the survey. The rest 382 were defined as the normotensive group. We compared the blood pressures of the hypertensive group with those of the normotensive group during pregnancy and postpartum. Then, 520 women were divided into quartiles (Q1-Q4) according to their blood pressures during pregnancy. After the changes in blood pressure for each gestational month relative to nonpregnant measurements were calculated, the changes in blood pressure were compared among the four groups. Additionally, the rate of developing hypertension was evaluated among the four groups. RESULTS: The average age of the participants was 54.8 years (range: 40-85 years) at the time of the study and 25.9 years (range: 18-44 years) at delivery. There were significant differences in blood pressure during pregnancy between the hypertensive group and the normotensive group. Meanwhile, these two groups did not indicate any differences in blood pressure in postpartum. Higher mean blood pressure during pregnancy was associated with smaller changes in blood pressure during pregnancy. The rate of development of hypertension in each group of systolic blood pressure was 15.9% (Q1), 24.6% (Q2), 29.7% (Q3), and 29.7% (Q4). The rate of development of hypertension in each group of diastolic blood pressure (DBP) was 18.8% (Q1), 24.6% (Q2), 22.5% (Q3), and 34.1% (Q4). CONCLUSIONS: Changes in blood pressure during pregnancy are small in women who have a higher risk of hypertension. Levels of blood pressure during pregnancy may be reflected in individual stiffness of blood vessels by the burden of pregnancy. If so, levels of blood pressure would be used to facilitate highly cost-effective screening and interventions for women with a high risk of cardiovascular diseases.