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Table 2 Demographic characteristics and FET parameters of the study population according to ongoing pregnancy

From: The timing for initiating estrogen stimulation in artificial cycle for frozen-thawed embryo transfer can be flexible

Parameters Ongoing pregnancy (n = 350) No ongoing pregnancy (n = 310) p value
Age, years 29 (27, 32) 30 (28, 34) 0.001
BMI, kg/m2 21.8 (20.1, 24.0) 22.2 (20.0, 25.0) 0.113
Infertility type, n (%) 0.751
 Primary 203 (58.0) 176 (56.8)  
 Secondary 147 (42.0) 134 (43.2)  
Infertility duration, years 3.5 (2, 5) 3 (2, 5) 0.549
Infertility factor, n (%) 0.349
 Tubal factor 164 (46.9) 124 (40.0)  
 Male factor 55 (15.7) 57 (18.4)  
 Mixed male and female factor 112 (32.0) 112 (36.1)  
 Unexplained 19 (5.4) 17 (5.5)  
Menstruation, n (%) 0.902
 Regular 188 (53.7) 168 (54.2)  
 Irregular 162 (46.3) 142 (45.8)  
Initial day of estrogen usage 11 (8, 13) 10 (7, 13) 0.387
Duration of estrogen usage, days 11 (10, 15) 11 (9, 15) 0.331
Endometrial thickness at initial day of estrogen, mm 5.0 (4.0, 5.7) 4.8 (4.1, 5.8) 0.879
Peak endometrial thickness, mm 8.5 (7.8, 9.6) 8.2 (7.6, 9.4) 0.076
Optimal embryos transferred, n (%) 321 (91.7) 251 (81.0) < 0.001
  1. The continuous data were expressed as median (lower and upper quartiles)