Characteristics Women Women Men Men
Group 1 (%)a Group 2 (%)b Group 1 (%)a Group 2 (%)b
Number of participants 5,422 (100.0) 2,467 (100.0) 5,422 (100.0) 2,467 (100.0)
Region
Anhui 1,317 (24.3) 450 (18.2)
Beijing 261 (4.8) 170 (6.9)
Fujian 853 (15.7) 130 (5.3)
Hebei 1,638 (30.2) 897 (36.4)
Heilongjiang 405 (7.5) 137 (5.6)
Nei Mongo 397 (7.3) 168 (6.8)
Zhejiang 551 (10.2) 515 (20.9)
P value <.01 <.01
Agec, years
20–24 2,297 (49.5) 856 (41.2) 1,150 (30.2) 440 (26.0)
25–29 1,617 (34.8) 704 (33.9) 1,570 (41.3) 616 (36.4)
30–34 463 (10.0) 179 (8.6) 632 (16.6) 226 (13.4)
35–39 234 (5.0) 315 (15.2) 370 (9.7) 347 (20.5)
≥40 33 (0.7) 24 (1.2) 83 (2.2) 62 (3.7)
Mean (SD) 25.6 (4.3) 26.4 (4.9) 27.6 (4.8) 28.5 (5.2)
P value <.01 <.01 <.01 <.01
Ethnicity
Han ethnic group 5,259 (97.4) 2,379 (97.3) 5,244 (98.0) 2,390 (98.3)
Minoritiesd 139 (2.6) 65 (2.7) 110 (2.1) 41 (1.7)
P value NS NS NS NS
Current BMI, kg/m2
<18.50 271 (5.0) 166 (6.8) 96 (1.8) 49 (2.0)
18.50–23.99 3,781 (70.3) 1,738 (71.0) 3,873 (72.4) 1,645 (68.0)
24.00–27.99 1,187 (22.1) 481 (19.7) 1,270 (23.7) 676 (28.0)
≥28.00 136 (2.5) 63 (2.6) 112 (2.1) 48 (2.0)
Mean (SD) 22.4 (2.5) 22.1 (2.6) 22.7 (2.2) 23.0 (2.2)
P value <.01 <.01 <.01 <.01
Education
Primary school and below 312 (5.8) 188 (7.6) 228 (4.3) 155 (6.4)
Middle school 3,307 (61.1) 1,527 (62.0) 3,255 (60.7) 1,519 (62.3)
High school 947 (17.5) 396 (16.1) 968 (18.1) 389 (15.9)
College and beyond 844 (15.6) 352 (14.3) 908 (16.9) 377 (15.5)
P value <.01 <.01 <.01 <.01
Occupation
Clerk 346 (6.4) 157 (6.4) 382 (7.1) 183 (7.5)
Professional worker 258 (4.8) 198 (8.1) 720 (13.4) 312 (12.8)
Service worker 553 (10.2) 438 (17.8) 1,063 (19.7) 407 (16.6)
Agricultural and related worker 1,491 (27.6) 688 (28.0) 1,591 (29.6) 750 (30.6)
Factory worker 111 (2.1) 92 (3.7) 743 (13.8) 308 (12.6)
Unemployed 2,408 (44.5) 599 (24.4) 46 (0.9) 33 (1.4)
Others or not stated 243 (4.5) 285 (11.6) 839 (15.6) 455 (18.6)
P value <.01 <.01 <.01 <.01
Annual household income, yuan
<10,000 3,214 (60.0) 1,298 (53.2)
10,000–19,999 1,288 (24.1) 602 (24.7)
>20,000 853 (15.9) 538 (22.1)
P value <.01 <.01
Toxic exposuree
Yes 73 (1.4) 90 (3.8) 163 (3.3) 131 (5.7)
No 5,176 (98.61) 2,291 (96.2) 4,860 (96.8) 2,169 (94.3)
P value <.01 <.01 <.01 <.01
Smoking
Yes 18 (0.3) 13 (0.5) 2,302 (42.7) 1,125 (45.7)
Nof 5,399 (99.7) 2,449 (99.5) 3,093 (57.3) 1,336 (54.3)
P value NS NS .01 .01
Drinking
Yes 88 (1.6) 40 (1.6) 2,492 (46.1) 1,138 (46.3)
Nog 5,324 (98.4) 2,417 (98.4) 2,914 (53.9) 1,320 (53.7)
P value NS NS NS NS
Physical exercise
Occasionally 4,551 (84.7) 1,992 (82.0)
2–3 times a month 632 (11.8) 344 (14.2)
At least once a week 193 (3.6) 94 (3.9)
P value <.01 <.01
Duration of cohabitation, yearsh Duration of cohabitation, yearsh Duration of cohabitation, yearsh Duration of cohabitation, yearsh Duration of cohabitation, yearsh Duration of cohabitation, yearsh
Mean (SD) 3.7 (3.7) 6.1 (4.8)
Menstrual cycle interval (day)i Menstrual cycle interval (day)i Menstrual cycle interval (day)i Menstrual cycle interval (day)i Menstrual cycle interval (day)i Menstrual cycle interval (day)i
≤23 375 (7.0) 213 (8.9)
24–35 4,798 (89.7) 1,953 (81.4)
>35 155 (2.9) 215 (8.9)
Others or not stated 23 (0.4) 19 (0.8)
P value <.01 <.01
History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy History of abnormal pregnancy
No 4,851 (89.5) 2,120 (85.9)
Yes 571 (10.5) 347 (14.1)
P value <.01 <.01
Parity
Nullipara 3,629 (66.9) 1,751 (71.0)
Multipara 1,793 (33.1) 716 (29.0)
P value <.01 <.01