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Table 1 Distribution of selected characteristics of the study population

From: Exposure to cooking fuels and birth weight in Lanzhou, China: a birth cohort study

Characteristic LBW NBW P SGA AGA P
N (%) N (%)   N (%) N (%)
Maternal age (years)       
 <25 164(25.2) 1344(15.7)   161(21.6) 1256(16.2)  
 25–29 227(34.9) 4205(49.0)   318(42.6) 3765(48.4)  
 ≥30 259(39.9) 3032(35.3) <0.001 267(35.8) 2754(35.4) <0.001
Highest education level       
 High school or less 414(63.7) 3230(37.6)   399(53.5) 2972(38.2)  
 College or above 219(33.7) 5196(60.6) <0.001 333(44.6) 4656(59.9) <0.001
 Missing 17(2.6) 155(1.8)   14(1.9) 147(1.9)  
Family income (RMB per capita)       
 <3000 436(67.1) 4233(49.3)   452(60.6) 3879(49.9)  
 ≥3,000 154(23.7) 3525(41.1) <0.001 216(28.9) 3164(40.7) <0.001
 Missing 60(9.2) 823(9.6)   78(10.5) 732(9.4)  
Maternal pre-pregnancy BMI (kg/m2)       
 ≤18.5 135(20.8) 1822(21.2)   189(25.3) 1670(21.5)  
 18.6–23.9 396(60.9) 5645(65.8)   445(59.7) 5122(65.9)  
 ≥24 79(12.1) 843(9.8) 0.078 77(10.3) 732(9.4) 0.010
 Missing 40(6.2) 273(3.2)   35(4.7) 251(3.2)  
Maternal weight gain during pregnancy (kg)       
 <15 346(53.2) 2541(29.6)   313(42.0) 2415(31.1)  
 15–18.5 132(20.3) 2753(32.1)   215(28.8) 2468(31.7)  
 >18.5 108(16.6) 2973(34.6) <0.001 171(22.9) 2590(33.3) <0.001
 Missing 64(9.9) 314(3.7)   47(6.3) 302(3.9)  
Vitamin supplement during pregnancy       
 No 150(23.1) 1234(14.4)   152(20.4) 1124(14.5)  
 Yes 486(74.8) 7259(84.6) <0.001 581(77.9) 6564(84.4) <0.001
 Missing 14(2.1) 90(1.0)   13(1.7) 87(1.1)  
Smoking (Active and passive)       
 No 489(75.2) 6923(80.7)   560(75.1) 6272(80.7)  
 Yes 161(24.8) 1658(19.3) <0.001 186(24.9) 1502(19.3) <0.001
Alcohol during pregnancy       
 No 641(98.6) 8490(98.9)   735(98.5) 7693(98.9)  
 Yes 2(0.3) 17(0.2) 0.882 2(0.3) 15(0.2) 0.989
 Missing 7(1.1) 74(0.9)   9(1.2) 67(0.9)  
Gestational Diabetes       
 No 647(99.5) 8513(99.2)   743(99.6) 7717(99.2)  
 Yes 3(0.5) 68(0.8) 0.485 3(0.3) 58(0.8) 0.368
Preeclampsia       
 No 539(82.9) 8388(97.8)   659(88.3) 7582(97.5)  
 Yes 111(17.1) 193(2.2) <0.001 87(11.7) 193(2.5) <0.001
Parity       
 Primiparous 379(58.5) 6375(74.3)   518(69.4) 5734(73.8)  
 Multiparous 269(41.5) 2208(25.7) <0.001 228(30.6) 2041(26.2) 0.012
Caesarean section       
 No 298(45.8) 5473(63.8)   400(53.6) 4978(64.0)  
 Yes 326(50.2) 3058(35.6) <0.001 335(44.9) 2739(35.2) <0.001
 Miss 26(4.0) 50(0.6)   11(1.5) 58(0.8)  
Gender       
 Boy 326(50.2) 4427(51.6)   369(49.5) 4067(52.3)  
 Girl 322(49.5) 4138(48.2)   376(50.4) 3693(47.5)  
 Missing 2(0.3) 16(0.2) 0.498 1(0.1) 15(0.2) 0.133
Ventilation       
 No 271(41.7) 1646(19.2)   249(33.4) 1563(20.1)  
 Yes 379(58.3) 6935(80.8) <0.001 497(66.6) 6212(79.9) <0.001