OBJECTIVETo study the longitudinal changes of blood pressure (BP) and its related determinants before and during normal pregnancy.

METHODS14 townships were randomly selected by cluster random sampling method from 37 townships in Liuyang city, Hunan province. Subjects are all women at childbearing age in these 14 townships registered from April 2008 to December 2011. When the subjects visited to the local maternity and child-care agencies for pre-marital check, they were face-to-face interviewed and asked to fill out the questionnaire and finish the medical examination. Following-up program was carried out until delivery, with BP and other pregnancy information checked and collected. Analysis on variance of data regarding repeated measurements were used to investigate the changes of BP and related determinants.

RESULTSA total of 611 cases with complete data were recruited, after excluding 41 cases who were diagnosed as pregnancy-induced hypertension. Finally, data on 570 healthy women with singleton pregnancies was analyzed. Systolic blood pressure (SBP) at pre-pregnancy, first trimester, second trimester and third trimester were (109.9 ± 12.9) mm Hg, (100.6 ± 9.6) mm Hg, (102.6 ± 10.1) mm Hg, (107.8 ± 10.9) mm Hg, respectively while the diastolic blood pressure (DBP) of pre-pregnancy, first trimester, second trimester and third trimester were (71.1 ± 9.0) mm Hg, (64.3 ± 6.6) mm Hg, (65.1 ± 6.8) mm Hg, (68.3 ± 8.1) mm Hg, respectively. The pre-pregnancy BP was lower than the three periods after pregnancy. BP of the third trimester was higher than that of the ones at first or second trimesters, with the difference statistically significant. SBP and DBP both indicated that there were statistically significant changes in the four periods and the linear trend test showed statistically significant. Pre-pregnancy BMI, pre-pregnancy waist circumference and annual per capita income were determinants which affecting the changes of BP. Higher pre-pregnancy body mass index (BMI), wider pre-pregnancy waist circumference and higher annual per capita income were associated with higher BP, while annual per capita income mainly affecting the pre-pregnancy BP.

CONCLUSIONBP of the three periods after pregnancy were lower than that of pre-pregnancy. BP of the third trimester was higher than both the first and second trimesters'. Pre-pregnancy BMI, pre-pregnancy waist circumference and annual per capita income were determinants which affecting the changes of BP.