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Table 1 Basic maternal and perinatal characteristics of the study population in relation to asthma ever

From: Maternal socioeconomic status and the risk of asthma among offspring

Characteristics No asthma N(%) Asthma N(%) pvalue
Maternal age, years    
 <20 1246(3.3) 69(2.7)  
 20-29 19 613(52.3) 1366(54.2)  
 30-39 15 544(41.3) 1015(40.3)  
 ≥40 1197(3.2) 68(2.7) 0.083
Maternal parity, primiparous 15 359(40.7) 967(38.4) 0.016
Maternal asthma 1016(2.7) 113(4.5) <0.001
Maternal gestational diabetes mellitus 2619(7.0) 143(5.7) 0.014
Maternal hypertension 716(1.9) 74(2.9) <0.001
Assisted reproduction technology, index pregnancy 1 1514(4.0) 142(5.6) <0.001
Pre-pregnancy BMI*, kg/m 2    
 <25 25 675(71.4) 1702(70.6)  
 25-29.9 7105(19.8) 480(19.9)  
 ≥30 3182(8.8) 228(9.5) 0.557
Marital status    
Unmarried 3938(10.5) 274(10.9)  
Married or cohabiting 33 662(89.5) 2244(89.1) 0.518
Socioeconomic status    
Upper white-collar worker 5375(14.3) 359(14.3)  
Lower white-collar worker 13 790(36.7) 973(38.6)  
Blue-collar worker 7528(20.0) 477(18.9)  
Entrepreneurs 1115(3.0) 52(2.1)  
Other 7582(20.2) 543(21.6)  
Missing 2210(5.9) 114(4.5) 0.001
Parental smoking**    
Non-smoking parents 19 215(55.2) 1240(52.3)  
Maternal/paternal smoking 8992(25.8) 633(26.7)  
Both smoking parents 6620(19.0) 498(21.0) 0.013
Mode of delivery    
 Vaginal 31 288(83.2) 2000(79.4)  
 Cesarean delivery 6312(16.8) 518(20.6) <0.001
Sex of child, boy 18 940(50.4) 1521(60.4) <0.001
Gestational age at birth, weeks    
 <28 129(0.3) 50(2.0)  
 28-32 341(0.9) 80(3.2)  
 33-36 1579(4.2) 149(5.9)  
 37-40 26 253(69.8) 1724(68.5)  
 ≥41 9298(24.7) 515(20.5) <0.001
Birth weight <2500 grams 1482(3.9) 221(8.8) <0.001
Small for gestational age (SGA) 13569(9.5) 263(10.4) 0.117
Asthma prevalence by age group, years    
 1-6 13 251(35.2) 445(17.7)  
 7-12 10 390(27.6) 945(37.5)  
 ≥13 13 959(37.1) 1128(44.8) <0.001
Mean age at the onset of asthma, years (±SD)   4.2(3.5)  
Total study population 37600(93.7) 2518(6.3)  
  1. 1Assisted reproduction technology before index pregnancy including in vitro fertilization, intra-cytoplasmic sperm injection, insemination and ovulation induction by clomifene citrate and other medicines.
  2. 2BMI: kilograms/square meters.
  3. *Body mass index, data missing 1746 (4.4%) cases.
  4. **Data missing 2920 (7.3%) cases.