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Table 2  Univariate logistic regression analyses of different variables with SSR

From: Associated factors of secondary sex ratio of offspring in assisted reproductive technology: a cross-sectional study in Jilin Province, China

Variables Total births Male babies SSR(%) OR 95%CI
Number of cycles
 1 ~ 3 2519 1272 50.50 1.000  
 4 ~ 6 29 13 44.83 0.797 0.382–1.663
Maternal age group
 20 ~ 29 892 441 49.44 1.000  
 30 ~ 39 1610 818 50.81 1.056 0.897–1.244
 ≥ 40 46 26 56.52 1.329 0.731–2.417
Paternal age group
 20 ~ 29 660 326 49.39 1.000  
 30 ~ 39 1661 839 50.51 1.046 0.873–1.25
 40 ~ 49 213 117 54.93 1.249 0.916–1.703
 50 ~ 59 14 3 21.43 0.279 0.077–1.011
Infertility duration
 0 ~ 10 2433 1222 50.23 1.000  
 11 ~ 20 115 63 54.78 1.201 0.825–1.748
Maternal BMI
 18.5 ~ 25 1723 876 50.58 1.000  
 < 18.5 593 286 48.23 0.901 0.747–1.086
 ≥ 25 232 123 53.02 1.091 0.829–1.436
Infertility type
 Primary 1766 898 50.85 1.000  
 Secondary 782 387 49.49 0.947 0.800-1.121
Infertility factor
 Male 987 483 48.94 1.000  
 Female 989 510 51.57 1.111 0.931–1.325
 Both male and female 368 183 49.73 1.032 0.812–1.311
 Unknown 204 109 53.43 1.197 0.885–1.619
Fertilization method
 IVF 1544 800 51.81 1.000  
 ICSI 822 380 46.23 0.800 0.675–0.947
 R-ICSI 182 105 57.69 1.268 0.930–1.730
Embryo transfer morphology
 Fresh 656 341 51.98 1.000  
 Thawed 1892 944 49.89 0.920 0.770–1.099
Number of embryos transferred
 1 214 117 54.67 1.000  
 2 2288 1149 50.22 0.836 0.631–1.108
 3 46 19 41.30 0.583 0.306–1.113
Embryo transfer stage
 Blastocyst 551 283 51.36 1.000  
 Cleavage stage 1997 1002 50.18 0.954 0.790–1.152
Birth type
 Singletons 2119 1060 50.02 1.000  
 Twins 429 225 52.45 1.102 0.895–1.356