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Table 2 Sex ratio among singleton live births stratified by different demographic characteristics and the embryo culture condition

From: Does the sex ratio of singleton births after frozen single blastocyst transfer differ in relation to blastocyst development?

Characteristic Singletons (n) Male (n) Sex ratio(%) P-value
Blastocyst quality     <0.001
 High 638 383 60.0  
 Poor 572 284 49.7  
Maternal age     0.261
 <35 971 543 55.9  
  ≥ 35 239 124 51.9  
Maternal BMI     0.173
 <18.5 47 32 68.1  
 18.5 ~ 24.9 772 425 55.1  
  ≥ 25 391 210 53.7  
Type of infertility     0.887
 Primary 541 297 54.9  
 Secondary 669 370 55.3  
Cause of infertility     0.537
 Female factor 661 363 54.9  
 Male factor 307 178 58  
 Combined factor 193 102 52.8  
 Unexplained 49 24 49  
Type of fertilization     0.191
 IVF 855 461 53.9  
 ICSI 355 206 58.0  
Day of frozen embryo     0.774
 D5 783 434 55.4  
 D6 427 233 54.6  
  1. Note: The sex ratio at birth is calculated as the proportion of males among all livebirths. P < 0.05 was considered statistically significant. CI = confidence interval; BMI = body mass index; D = day; IVF = in vitro fertilization; ICSI = intracytoplasmic sperm injection