Table 1 Descriptive characteristics of participants
From: Surrounding greenness is associated with lower risk and burden of low birth weight in Iran
Characteristic | No. (%) | |||
|---|---|---|---|---|
Total | Normal birth weight | Low birth weight | Term low birth weight | |
Subjects | 4,021,741 | 3,758,013 (93.4) | 263,728 (6.6) | 121,852 (3.0) |
Birth weight (grams, mean ± SD) | 3176.2 ± 503.2 | 3257.0 ± 394.0 | 2024.8 ± 479.2 | 2196.7 ± 407.9 |
Gestational age (weeks, mean ± SD) | 38.5 ± 1.7 | 38.7 ± 1.2 | 35.4 ± 3.5 | 38.3 ± 1.0 |
Infant sex | ||||
Male | 2,074,664 (51.6) | 1,951,484 (51.9) | 123,180 (46.7) | 51,039 (41.9) |
Female | 1,947,077 (48.4) | 1,806,529 (48.1) | 140,548 (53.3) | 70,813 (58.1) |
Season of birth | ||||
Spring | 976,828 (24.3) | 909,836 (24.2) | 66,992 (25.4) | 30,936 (25.4) |
Summer | 1,140,987 (28.4) | 1,066,848 (28.4) | 74,139 (28.1) | 34,309 (28.2) |
Autumn | 980,745 (24.4) | 917,468 (24.4) | 63,277 (24.0) | 28,891 (23.7) |
Winter | 923,181 (23.0) | 863,861 (23.0) | 59,320 (22.5) | 27,716 (22.7) |
Number of fetuses | ||||
Singleton | 3,976,387 (98.9) | 3,738,825 (99.5) | 237,562 (90.1) | 115,228 (94.6) |
Multiple gestations | 45,354 (1.1) | 19,188 (0.5) | 26,166 (9.9) | 6624 (5.4) |
Maternal age, yrs | ||||
≤25 | 1,453,336 (36.1) | 1,358,339 (36.1) | 94,997 (36.0) | 46,289 (38.0) |
(25, 35] | 2,133,831 (53.1) | 1,999,070 (53.2) | 134,761 (51.1) | 61,375 (50.4) |
>35 | 434,574 (10.8) | 400,604 (10.7) | 33,970 (12.9) | 14,188 (11.6) |
Parity | ||||
0 | 1,670,615 (41.5) | 1,543,838 (41.1) | 126,777 (48.1) | 59,097 (48.5) |
≥1 | 2,351,126 (58.5) | 2,214,175 (58.9) | 136,951 (51.9) | 62,755 (51.5) |
Residence | ||||
City | 3,097,265 (77.0) | 2,897,059 (77.1) | 200,206 (75.9) | 90,849 (74.6) |
Village | 924,476 (23.0) | 860,954 (22.9) | 63,522 (24.1) | 31,003 (25.4) |
Education attainment | ||||
Below high school | 1,927,541 (47.9) | 1,791,513 (47.7) | 136,028 (51.6) | 63,459 (52.1) |
High school | 1,206,248 (30.0) | 1,133,219 (30.2) | 73,029 (27.7) | 34,050 (27.9) |
College or above | 887,952 (22.1) | 833,281 (22.2) | 54,671 (20.7) | 24,343 (20.0) |
Nationality | ||||
Iranian | 3,873,207 (96.3) | 3,619,299 (96.3) | 253,908 (96.3) | 117,106 (96.1) |
Non-Iranian | 148,534 (3.7) | 138,714 (3.7) | 9820 (3.7) | 4746 (3.9) |
Delivery type | ||||
Cesarean section | 2,059,655 (51.2) | 1,903,604 (50.7) | 156,051 (59.2) | 66,019 (54.2) |
Vaginal delivery | 1,962,086 (48.8) | 1,854,409 (49.3) | 107,677 (40.8) | 55,833 (45.8) |
Delivery complications | ||||
Absent | 3,914,965 (97.3) | 3,657,444 (97.3) | 257,521 (97.6) | 119,018 (97.7) |
Present | 106,776 (2.7) | 100,569 (2.7) | 6207 (2.4) | 2834 (2.3) |
Diabetes | ||||
Absent | 3,919,203 (97.5) | 3,663,529 (97.5) | 255,674 (96.9) | 119,238 (97.9) |
Present | 102,538 (2.5) | 94,484 (2.5) | 8054 (3.1) | 2614 (2.1) |
Chronic hypertension | ||||
Absent | 3,959,776 (98.5) | 3,704,473 (98.6) | 255,303 (96.8) | 119,196 (97.8) |
Present | 61,965 (1.5) | 53,540 (1.4) | 8425 (3.2) | 2656 (2.2) |
Environmental exposures | ||||
NDVI−500m | 0.313 ± 0.21 | 0.315 ± 0.21 | 0.287 ± 0.21 | 0.276 ± 0.20 |
NDVI−1000m | 0.314 ± 0.20 | 0.316 ± 0.20 | 0.288 ± 0.20 | 0.276 ± 0.20 |
NDVI−2000m | 0.315 ± 0.20 | 0.317 ± 0.20 | 0.290 ± 0.19 | 0.278 ± 0.19 |
NDVI−3000m | 0.317 ± 0.19 | 0.319 ± 0.19 | 0.292 ± 0.19 | 0.280 ± 0.19 |
EVI−500m | 0.225 ± 0.16 | 0.227 ± 0.16 | 0.207 ± 0.15 | 0.200 ± 0.15 |
EVI−1000m | 0.226 ± 0.15 | 0.227 ± 0.15 | 0.207 ± 0.15 | 0.199 ± 0.15 |
EVI−2000m | 0.227 ± 0.15 | 0.228 ± 0.15 | 0.209 ± 0.14 | 0.201 ± 0.14 |
EVI−3000m | 0.229 ± 0.14 | 0.230 ± 0.14 | 0.210 ± 0.14 | 0.202 ± 0.14 |
PM2.5, μg/m3 | 41.1 ± 12.6 | 41.1 ± 12.6 | 41.9 ± 12.9 | 42.2 ± 12.4 |
Temperature, °C | 16.7 ± 5.8 | 16.7 ± 5.7 | 17.0 ± 6.3 | 17.3 ± 6.0 |
Relative humidity, % | 43.5 ± 13.3 | 43.5 ± 13.2 | 42.4 ± 13.7 | 41.6 ± 13.1 |
