Table 1 Summary of Study Participants’ Characteristics and Birthweight Outcome and Meteorology Variables (N = 14220)
Characteristics | Mean (SD) or n (%) | |
|---|---|---|
Birthweight Outcomes | Â | |
Birthweight (g), mean (SD) | 3358.7 | (402.0) |
Z-score, mean (SD) | 0.2 | (1.0) |
Small for gestational age (SGA), n (%) | 820 | (5.8%) |
Large for gestational age (LGA), n (%) | 1819 | (12.8%) |
Maternal variables | Â | Â |
Maternal age in years during first antenatal visit | 33.4 | (3.8) |
 Age < = 25 | 111 | (0.8%) |
 25 < Age < = 30 | 2823 | (19.9%) |
 30 < Age < = 35 | 7646 | (53.8%) |
 35 < Age | 3640 | (25.5%) |
Maternal ethnicity, n (%) | Â | Â |
 Han | 6885 | (48.4%) |
 Other ethnic minority | 129 | (0.9%) |
 Not reported | 7206 | (50.7%) |
Education level, n (%) | Â | Â |
 High school or less | 1155 | (8.1%) |
 College/undergraduate level | 9703 | (68.2%) |
 Above college | 2344 | (16.5%) |
 Not reported | 1017 | (7.2%) |
Number of deliveries before, n (%) | Â | Â |
 Zero | 10,962 | (77.1%) |
 One | 3199 | (22.5%) |
 Two or above | 59 | (0.4%) |
Maternal first trimester BMI, mean (SD) | 20.7 | (4.4) |
Maternal first trimester BMI category, n (%) | Â | Â |
 BMI < 18.5 kg/m2 | 1921 | (13.5%) |
 18.5 kg/m2 <=BMI < 24 kg/m2 | 10,360 | (72.9%) |
 24 < = BMI < 28 kg/m2 | 1577 | (11.1%) |
 BMI > = 28 kg/m2 | 362 | (2.5%) |
Active smoking between preconception and early pregnancy, n (%) | Â | Â |
 Yes | 155 | (1.1%) |
 No | 13,085 | (92.0%) |
 Missing | 980 | (6.9%) |
Environmental smoking between preconception and early pregnancy, n (%) | Â | Â |
 Yes | 2318 | (16.3%) |
 No | 10,911 | (76.7%) |
 Missing | 991 | (7.0%) |
Occupation, n (%) | Â | Â |
 Worker/ office clerk / Self-employed | 8257 | (58.1%) |
 Manager/Technician/Entrepreneur | 4834 | (34.0%) |
 Missing/unemployed | 1129 | (7.9%) |
Folic acid supplementation during preconception and early pregnancy | Â | Â |
 Yes | 9963 | (70.1%) |
 No | 4257 | (29.9%) |
Children variable | Â | Â |
Birth season, n (%) | Â | Â |
 Spring (March ‒ May) | 3253 | (22.9%) |
 Summer (June ‒ August) | 3514 | (24.7%) |
 Fall (September ‒ November) | 4189 | (29.5%) |
 Winter (December ‒ February) | 3264 | (23.0%) |
Delivery mode | Â | Â |
 Vaginal birth | 8650 | (60.8%) |
 Caesarean section | 5570 | (39.2%) |
Birth term/gestational age (weeks), mean (SD) | 39.2 | (1.1) |
Children’s sex |  |  |
 Male | 8070 | (56.8%) |
 Female | 6150 | (43.2%) |