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Table 1 Characteristics of women by preterm birth (< 37 weeks gestational age)

From: Fertility treatments and the risk of preterm birth among women with subfertility: a linked-data retrospective cohort study

  Term (> 37 weeks) Preterm (< 37) Total P value
N Row% N Row% N Col%
Maternal age at delivery        
 ≤ 30 290 81.7% 65 18.3% 355 72.4% 0.669
 31+ 108 80.0% 27 20.0% 135 27.6%  
Paternal age at delivery        
 ≤ 30 239 83.0% 49 17.0% 288 58.9% 0.223
 31+ 158 78.6% 43 21.4% 201 41.1%  
BMI category (pre-pregnancy)        
 Underweight/Normal 184 76.0% 58 24.0% 242 55.1% 0.148
 Overweight/Obese 161 81.7% 36 18.3% 197 4.9%  
Income (at interview)        
 Less than $50,000 110 81.5% 25 18.5% 135 28.7% 0.938
 50,000–$99,999 213 80.1% 53 19.9% 266 56.6%  
 Over $100,000 56 81.2% 13 18.8% 69 14.7%  
Education level (at interview)        
 Less than college grad 127 77.4% 37 22.6% 164 33.6% 0.136
 College grad or more 269 83.0% 55 17.0% 324 66.4%  
Race/Ethnicity        
 White, non-Hispanic 381 80.9% 90 19.1% 471 96.1% 0.348
 Hispanic, other non-White 17 89.5% 2 10.5% 19 3.9%  
Religion        
 Non-LDS 84 78.5% 23 21.5% 107 21.8% 0.415
 Latter-day Saint 314 82.0% 69 18.0% 383 78.2%  
Attempt duration to conception        
 < 12 months 69 81.2% 16 18.8% 85 17.4% 0.771
 12 to < 24 100 81.3% 23 18.7% 123 25.2%  
 24 to < 36 73 85.9% 12 14.1% 85 17.4%  
 36 to < 48 58 79.5% 15 20.5% 73 14.9%  
 48+ 97 78.9% 26 21.1% 123 25.2%  
Recruitment cohort        
 Clinic 203 76.3% 63 23.7% 266 54.3% 0.002
 Population 195 87.1% 29 12.9% 224 45.7%  
Baby sex        
 F 188 79.0% 50 21.0% 238 48.6% 0.219
 M 210 83.3% 42 16.7% 252 51.4%  
Multiplicity        
 Singleton 374 90.8% 38 9.2% 412 84.1% 0.000
 Twins 24 33.8% 47 66.2% 71 14.5%  
 Triplets 0 0.0% 7 100.0% 7 1.4%  
Treatment in cycle of conception        
 None 190 89.2% 23 10.8% 214 43.5% 0.001
 Drugs 61 79.2% 16 20.8% 77 15.7%  
 IUI 48 75.0% 16 25.0% 64 13.1%  
 IVF 99 72.8% 37 27.2% 136 27.8%  
Total 398 81.2% 92 18.8% 490 100.0%