Table 1 Basic characteristics of low birth weight cases and controls [n (%)]
From: Maternal urinary manganese and risk of low birth weight: a case–control study
Characteristics | Cases (n = 204) | Controls (n = 612) |
|---|---|---|
Infant sex | ||
Male | 101 (49.5) | 303 (49.5) |
Female | 103 (50.5) | 309 (50.5) |
Maternal age | ||
< 25 years | 48 (23.5) | 146 (23.8) |
25–29 years | 81 (39.7) | 242 (39.5) |
≥ 30 years | 75 (36.7) | 224 (36.6) |
Education | ||
≤ 9 years | 89 (43.6) | 167 (27.3) |
9–12 years | 38 (18.6) | 120 (19.6) |
> 12 years | 77 (37.8) | 322 (52.6) |
Missing | 0 (0.0) | 3 (0.5) |
Household income | ||
< 50,000 yuan per year | 116 (56.9) | 275 (44.9) |
≥ 50,000 yuan per year | 61 (29.9) | 279 (45.6) |
Missing | 27 (13.2) | 58 (9.5) |
Parity | ||
Primiparous | 159 (77.9) | 501 (81.9) |
Multiparous | 45 (22.1) | 111 (18.1) |
Gestational hypertension | ||
Yes | 20 (9.8) | 12 (2.0) |
No | 183 (89.7) | 598 (97.7) |
Missing | 1 (0.5) | 2 (0.3) |
Gestational diabetes | ||
Yes | 7 (3.4) | 27 (4.4) |
No | 197 (96.6) | 585 (95.6) |
Pre-pregnancy BMI | ||
< 18.5 kg/m2 | 60 (29.4) | 125 (20.4) |
18.5–23.9 kg/m2 | 108 (52.9) | 385 (62.9) |
≥ 24 kg/m2 | 26 (12.8) | 85 (13.9) |
Missing | 10 (4.9) | 17 (2.8) |
Multivitamin supplement during pregnancy | ||
Yes | 137 (67.2) | 409 (66.8) |
No | 59 (28.9) | 190 (31.1) |
Missing | 8 (3.9) | 13 (2.1) |
Smoking during pregnancy | ||
No | 198 (97.1) | 608 (99.4) |
Yes | 1 (0.5) | 0 (0.0) |
Missing | 5 (2.4) | 4 (0.6) |
Passive smoking during pregnancy | ||
Yes | 47 (23.0) | 129 (21.1) |
No | 149 (73.0) | 464 (75.8) |
Missing | 8 (3.9) | 19 (3.1) |
Alcohol use during pregnancy | ||
Yes | 2 (1.0) | 1 (3.3) |
No | 196 (96.1) | 594 (97.1) |
Missing | 6 (2.9) | 17 (2.8) |