Table 1 Baseline characteristics of cohort participants

INFANT CHARACTERISTICS (N)

2633

1685

4318

Sex²

  Male

1397 (53.1%)

843 (50.1%)

2240 (51.9%)

  Female

1236 (46.9%)

840 (49.9%)

2076 (48.1%)

Gestational age at birth²

  <37 weeks

85 (3.2%)

33 (2.0%)

118 (2.7%)

  ≥ 37 weeks

2548 (96.8%)

1645 (98.0%)

4193 (97.3%)

Method of delivery²

  Vaginal

1651 (62.7%)

1561 (92.8%)

3212 (74.4%)

  Caesarean

982 (37.3%)

122 (7.2%)

1104 (25.6%)

Birthweight²

  <2500 grams

134 (5.1%)

78 (4.6%)

212 (4.9%)

  ≥ 2500 grams

2499 (94.9%)

1605 (95.4%)

4104 (95.1%)

Siblings

  0

1497 (56.9%)

1081 (64.2%)

2578 (59.7%)

  1

917 (34.8%)

498 (29.6%)

1415 (32.8%)

  ≥ 2

219 (8.3%)

106 (6.3%)

325 (7.5%)

Breastfeeding after birth³

  Exclusive breastfeeding

296 (11.2%)

1179 (70.1%)

1475 (34.2%)

  Breastfeeding and formula

1895 (72.0%)

491 (29.2%)

2386 (55.3%)

  No breastfeeding

442 (16.8%)

12 (0.7%)

454 (10.5%)

Admitted to neonatal ward after birth²

  No

2547 (96.7%)

1667 (99.0%)

4214 (97.6%)

  Yes

86 (3.3%)

16 (1.0%)

102 (2.4%)

Mother’s characteristics

Ethnicity²

  Kinh

2456 (93.3%)

1681 (99.8%)

4137 (95.9%)

  Other

176 (6.7%)

3 (0.2%)

179 (4.1%)

Marital status¹

  Currently married

2578 (97.9%)

1674 (99.3%)

4252 (98.5%)

  Other

54 (2.1%)

11 (0.7%)

65 (1.5%)

Highest education level attained¹

  No school/some primary school

328 (12.5%)

310 (18.4%)

638 (14.8%)

  Completed primary school

1362 (51.7%)

987 (58.6%)

2349 (54.4%)

  Completed secondary school

545 (20.7%)

233 (13.8%)

778 (18.0%)

  Completed university/postgraduate

397 (15.1%)

155 (9.2%)

552 (12.8%)

Occupation¹

  Stay at home

967 (36.7%)

495 (29.4%)

1462 (33.9%)

  Professionals and technicians

182 (6.9%)

141 (8.4%)

323 (7.5%)

  Service and sales

897 34.1%)

154 (9.1%)

1051 (24.3%)

  Agriculture, craft and trades

490 (18.6%)

489 (29.0%)

979 (22.7%)

  Elementary occupations

58 (2.2%)

241 (14.3%)

299 (6.9%)

  Other occupations

35 (1.3%)

162 (9.6%)

197 (4.6%)

  Unemployed

3 (0.1%)

3 (0.2%)

6 (0.1%)

Characteristic, cont.

HCMC

Dong Thap

Total

Number of pregnancies¹

  1

1129 (42.9%)

938 (55.7%)

2067 (47.9%)

  2

836 (31.8%)

476 (28.2%)

1312 (30.4%)

  ≥ 3

667 (25.3%)

271 (16.1%)

938 (21.7%)

Age at this delivery

  median (IQR)

27 (24 – 32)

25 (21 – 29)

26 (23 – 31)

Age at first childbirth

  median (IQR)

25 (21 – 28)

23 (20 – 25)

24 (21 – 27)

Exposure to passive cigarette smoke²

  No

1463 (55.6%)

851 (50.5%)

2314 (53.6%)

  Yes

1169 (44.4%)

827 (49.1%)

1996 (46.2%)

  Don’t know

0

6 (0.4%)

6 (0.1%)

Household characteristics

Household crowding (people/room)

  median (IQR)

2.3 (1.7 – 3.0)

3.0 (2.0 – 4.0)

2.5 (1.7 – 3.0)

Main source of drinking water³

  Bottled

749 (28.5%)

116 (6.9%)

865 (20.0%)

  Piped (own residence)

1789 (68.0%)

525 (31.2%)

2314 (53.6%)

  Piped (public tap)

45 (1.7%)

173 (10.3%)

218 (5.1%)

Well

46 (1.7%)

21 (1.2%)

67 (1.6%)

  Rain/spring/river/stream

3 (0.1%)

848 (50.4%)

851 (19.7%)

Water treated before drinking^2*

  No

39 (2.1%)

4 (0.3%)

43 (1.3%)

  Boiled

1635 (86.8%)

1158 (73.9%)

2793 (80.9%)

  Filtered

206 (10.9%)

394 (25.1%)

600 (17.4%)

  Other treatment

3 (0.2%)

12 (0.8%)

15 (0.4%)

Main household fuel⁴

  Gas/electricity

2512 (95.5%)

809 (48.1%)

3321 (77.0%)

  Wood/coal/straw

46 (1.7%)

869 (51.6%)

915 (21.2%)

  Kerosene

73 (2.8%)

5 0.3%)

78 (1.8%)

Keep pigs in household¹

  No

2619 (99.5%)

1509 (89.6%)

4128 (95.6%)

  Yes

13 (0.5%)

176 (10.4%)

189 (4.4%)

Keep birds or poultry in household²

  No

2571 (97.7%)

1147 (68.1%)

3718 (86.1%)