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Table 1 Characteristics of sample stratified by educational level

From: BMI mediates the association between low educational level and higher blood pressure during pregnancy in Japan

Characteristics All (n= 923) Low (n=228)* Mid (n=228)* High (n=467)* Pvalue
Maternal age (yrs) 33.7 (4.1) 33.4 (4.7) 34.1 (4.1) 33.6 (3.8) NS
Pre-pregnancy BMI (kg/m2) 20.2 (2.3) 21.0 (2.9) 20.1 (2.2) 19.8 (2.0) <0.0001
BMI>25, n(%) 41 (4.4) 19 (8.3) 10 (4.4) 12 (2.6) <0.05
BMI>30, n(%) 3 (0.3) 2 (0.9) 1 (0.4) 0 (0) NS
Parity      
0, n(%) 452 (49.0) 97 (42.5) 104 (45.6) 251 (53.8) <0.0001
1, n(%) 471 (51.0) 131 (57.5) 124 (54.4) 216 (46.2)
Mean gestational age before 16 weeks blood pressure 14.3 (0.98) 14.3 (0.98) 14.3 (0.98) 14.3 (1.0) NS
Mean gestational age at 20 weeks blood pressure 20 (1.2) 19.9 (1.2) 20.1 (1.2) 20.0 (1.1) NS
Maternal pre-pregnancy complications      
Diabetes mellitus, n(%) 5 (0.5) 3 (1.3) 1 (0.44) 1 (0.21) NS
Hypertension, n(%) 5 (0.5) 0 (0.0) 4 (1.8) 1 (0.21) <0.05
Renal disease, n(%) 4 (0.4) 1 (0.4) 1 (0.44) 2 (0.43) NS
Pre-pregnancy complications      
PIH, n(%) 11 (1.2) 4 (1.8) 1 (0.44) 6 (1.3) NS
Family History      
Diabetes mellitus, n(%) 72 (7.8) 14 (6.1) 19 (8.3) 39 (8.4) NS
Hypertension, n(%) 69 (7.5) 13 (5.7) 14 (6.1) 42 (9.0) NS
Smoking      
Never or former, n(%) 891 (96.9) 209 (92.5) 224 (98.7) 458 (98.1) <0.001
Current, n(%) 29 (3.2) 17 (7.5) 3 (1.3) 9 (1.9)
Income (per year), n(%)      
<4 million yen 49 (5.7) 23 (10.6) 10 (4.8) 16 (3.7) <0.001
<6 million yen 199 (23.2) 78 (35.9) 50 (24.2) 71 (16.4)
<8 million yen 189 (22.1) 56 (25.8) 47 (22.7) 86 (19.9)
<10 million yen 185 (21.6) 34 (15.7) 44 (21.3) 107 (24.7)
over 10 million yen 235 (27.4) 26 (12.0) 56 (27.1) 153 (35.3)
Salt Intake      
low, n(%) 302 (34.1) 81 (37.7) 66 (30.0) 155 (34.3) NS
moderate, n(%) 295 (33.3) 65 (30.2) 72 (32.7) 158 (35.0)
high, n(%) 290 (32.7) 69 (32.1) 82 (37.3) 139 (30.8)
Alcohol Intake      
None or former, n(%) 749 (84.4) 183 (85.1) 192 (87.3) 374 (82.7) NS
Current, n(%) 138 (15.6) 32 (14.9) 28 (12.7) 78 (17.3)
Body weight gain until midpregnancy (kg) 3.4 (2.5) 3.9 (2.9) 2.9 (2.6) 3.4 (2.2) <0.001
  1. Values are given as mean ± standard deviation for continuous variables.
  2. PIH, pregnancy-induced hypertension; BMI, body mass index; NS, not significant; SD, standard deviation.
  3. *”Low” denotes vocational training school, high school, or less; “Mid” denotes junior college; “High” denotes college or more than college.