Table 1 The distribution of maternal and fetus characteristics among five ethnic groups: Yunnan, China, 2010-2018

Number

8,733

123,600

5,292

5,639

34,256

177,520

 Education level

< 0.001

  N-Miss

20

1,591

64

30

246

1,951

  Low

2,767 (31.8)

1,7696 (14.5)

1,733 (33.1)

2,990 (53.3)

9,255 (27.2)

34,441 (19.6)

  Middle

4,636 (53.2)

6,9643 (57.1)

2,514 (48.1)

2,203 (39.3)

18,391 (54.1)

97,387 (55.5)

  High

1,310 (15.0)

3,4670 (28.4)

981 (18.8)

416 (7.4)

6,364 (18.7)

43,741 (24.9)

 Parity

< 0.001

  N-Miss

17

375

21

11

90

514

  0

2,553 (29.3)

51,873 (42.1)

1,495 (28.4)

1,990 (35.4)

11,751 (34.4)

69,662 (39.4)

  1

3,752 (43.0)

48,116 (39.0)

1,896 (36.0)

2,297 (40.8)

13,417 (39.3)

69,478 (39.3)

  >1

2,411 (27.7)

23,236 (18.9)

1,880 (35.7)

1,341 (23.8)

8,998 (26.3)

37,866 (21.4)

 Age

< 0.001

  N-Miss

26

146

11

32

25

240

  <20

334 (3.8)

3,236 (2.6)

231 (4.4)

880 (15.7)

1,134 (3.3)

5,815 (3.3)

  20-35

7,979 (91.6)

112,455 (91.1)

4,663 (88.3)

4,393 (78.3)

31,259 (91.3)

160,749 (90.7)

  ≥35

394 (4.5)

7,763 (6.3)

387 (7.3)

334 (6.0)

1,838 (5.4)

10,716 (6.0)

 Birth order

< 0.001

  N-miss

17

375

21

11

90

514

  1

3,681 (42.2)

62,506 (50.7)

2,176 (41.3)

2,307 (41.0)

15,509 (45.4)

86,179 (48.7)

  2

4,901 (56.2)

59,077 (47.9)

2,897 (55.0)

3,074 (54.6)

18,080 (52.9)

88,029 (49.7)

  >3

134 (1.5)

1,642 (1.3)

198 (3.8)

247 (4.4)

577 (1.7)

2,798 (1.6)

 Work

< 0.001

  N-Miss

37

1,226

58

63

227

1,611

  Farmer

8,390 (96.5)

111,618 (91.2)

4,965 (94.9)

5,459 (97.9)

32,605 (95.8)

163,037 (92.7)

  Non-farmer

306 (3.5)

10,756 (8.8)

269 (5.1)

117 (2.1)

1,424 (4.2)

12,872 (7.3)

 BMI (kg/m²)

< 0.001

  N-Miss

3

232

6

4

38

283

  Underweight

1,553 (17.8)

16,969 (13.8)

632 (12.0)

429 (7.6)

4,174 (12.2)

23,757 (13.4)

  Normal weight

6,145 (70.4)

93,793 (76.0)

3,946 (74.7)

4,678 (83.0)

26,382 (77.1)

134,944 (76.1)

  Overweight

877 (10.0)

11,179 (9.1)

597 (11.3)

471 (8.4)

3,176 (9.3)

16,300 (9.2)

  Obese

155(1.8)

1,427 (1.2)

111 (2.1)

57 (1.0)

486 (1.4)

2,236 (1.3)

 N-miss

3

232

6

4

38

283

 <150

1,397 (16.0)

10,827 (8.8)

917 (17.3)

1,998 (35.5)

4,181 (12.2)

19,320 (10.9)

 ≥150

7,333 (84.0)

112,541 (91.2)

4,369 (82.7)

3,637 (64.5)

30,037 (87.8)

157,917 (89.1)

Maternal disease ^a

< 0.001

 N-Miss

71

981

64

31

286

1,433

 Yes

261 (3.0)

1,579 (1.3)

101 (1.9)

42 (0.7)

388 (1.1)

2,371 (1.3)

Economic stress

< 0.001

 N-Miss

51

700

39

31

187

1,008

 Never

6,705 (77.2)

91,354 (74.3)

3,249 (61.9)

4,546 (81.1)

24,572 (72.1)

130,426 (73.9)

 Slightly

1,157 (13.3)

18,704 (15.2)

1,023 (19.5)

606 (10.8)

5,317 (15.6)

26,807 (15.2)

 Considerable

820 (9.4)

12,842 (10.4)

981 (18.7)

456 (8.1)

4,180 (12.3)

19,279 (10.9)

 Induced abortion

< 0.001

  Yes

2,845 (32.6)

26,052 (21.1)

1,998 (37.8)

1,239 (22.0)

10,137 (29.6)

42,271 (23.8)

  Missing

2,537 (29.1)

45,518 (36.8)

1,433 (27.1)

1,971 (35.0)

10,998 (32.1)

62,457 (35.2)

 Natural abortion

< 0.001

  Yes

356 (4.1)

4,139 (3.3)

302 (5.7)

195 (3.5)

1,298 (3.8)

6,290 (3.5)

  Missing

2,537 (29.1)

45,520 (36.8)

1,433 (27.1)

1,971 (35.0)

10,998 (32.1)

62,459 (35.2)

 Stillbirth

< 0.001

  Yes

68 (0.8)

1,024 (0.8)

60 (1.1)

43 (0.8)

309 (0.9)

1,504 (0.8)

  Missing

2,537 (29.1)

45,520 (36.8)

1,433 (27.1)

1,971 (35.0)

10,998 (32.1)

62,459 (35.2)

 Folate use

< 0.001

  N-Miss

14

784

31

51

192

1,072

  Unused

420 (4.8)

5,092 (4.1)

464 (8.8)

351 (6.3)

1591 (4.7)

7,918 (4.5)

  Irregular Used

475 (5.5)

7,831 (6.4)

411 (7.8)

355 (6.4)

3,092 (9.1)

12,164 (6.9)

  Regular Used

7,824 (89.7)

109,893 (89.5)

4,386 (83.4)

4,882 (87.3)

29,381 (86.3)

156,366 (88.6)

 Smoking status

< 0.001

  N-Miss

69

953

48

39

247

1,356

  Smoke free

7,509 (86.7)

103,543 (84.4)

4,359 (83.1)

5,119 (91.4)

29,364 (86.3)

149,894 (85.1)

  Passive smoking (only)

1,130 (13.0)

18,635 (15.2)

856 (16.3)

473 (8.4)

4,570 (13.4)

25,664 (14.6)

  Smoker

25 (0.3)

469 (0.4)

29 (0.6)

8 (0.1)

75 (0.2)

606 (0.3)

 IUD use

< 0.001

  N-Miss

38

822

31

34

185

1,110

  Ever

2,450 (28.2)

26,417 (21.5)

1,164 (22.1)

1,010 (18.0)

8,161 (24.0)

39,202 (22.2)

 Fetus sex

0.007

  N-miss

23

259

7

9

87

385

  Female

4,216 (48.4)

58,905 (47.8)

2,464 (46.6)

2,596 (46.1)

16,469 (48.2)

84,650 (47.8)

  Male

4,463 (51.2)

63,924 (51.8)

2,807 (53.1)

3,002 (53.3)

17,577 (51.4)

91,773 (51.8)

  Unknown ^b

31 (0.4)

512 (0.4)

14 (0.3)

32 (0.6)

123 (0.4)

712 (0.4)

Preterm births ^c

667 (7.6)

6,235 (5.0)

351 (6.6)

364 (6.5)

1,607 (4.7)

9,224 (5.2)

< 0.001

Congenital anomalies

0.454

 N-Miss

23

261

7

9

87

387

 Yes

13 (0.1)

159 (0.1)

7 (0.1)

5 (0.1)

31 (0.1)

215 (0.1)

Stillbirth

90 (1.0)

705 (0.6)

37 (0.7)

31 (0.5)

223 (0.7)

1,086 (0.6)

< 0.001

 Female stillbirth

25 (0.3)

218 (0.2)

13 (0.2)

12 (0.2)

67 (0.2)

335 (0.2)

 Male stillbirth

33 (0.4)

261 (0.2)

13 (0.2)

9 (0.2)

90 (0.3)

406 (0.2)

 Sex-unknown ^b stillbirth

31 (0.4)

224 (0.2)

11 (0.2)

10 (0.2)

64 (0.2)

340 (0.2)

 Sex-missing stillbirth

1 (0.0)

2 (0.0)

0 (0.0)

0 (0.0)

2 (0.0)

5 (0.0)