Table 1 General clinical data
|  | Control (n = 4750) | RIF (n = 462) | t/X2 | P |
|---|---|---|---|---|
Female | Â | Â | Â | Â |
 Age (years) | 31.00 ± 3.66 | 33.30 ± 4.14 | 6.070 | 0.000 |
 Duration of infertility (years) | 2.70 ± 2.04 | 4.06 ± 2.79 | 5.721 | 0.000 |
 BMI (kg/m2) | 22.92 ± 3.13 | 22.42 ± 3.02 | 1.677 | 0.094 |
 Type of infertility   Primary infertility   Secondary infertility | 2590(54.53) 2160(45.47) | 191(41.34) 271(58.66) | 29.408 | 0.000 |
 Diagnosis of infertility |  |  |  |  |
  Tubal factor | 3220(67.79) | 272(58.87) | 15.135 | 0.000 |
  PCOS | 513(10.08) | 51(11.04) | 0.250 | 0.875 |
  DOR | 290(6.11) | 91(19.70) | 84.697 | 0.000 |
  Other ovarian factors | 105(2.21) | 7(1.52) | 0.968 | 0.325 |
  EMs | 430(9.05) | 76(16.45) | 26.286 | 0.000 |
 Number of induced abortions |  |  | 130.388 | 0.000 |
  0 | 3315(69.79) | 222(48.05) |  |  |
  1 | 1050(22.11) | 137(29.65) |  |  |
  ≥2 | 385(8.10) | 103(22.30) |  |  |
Male | Â | Â | Â | Â |
 Age (years)(X ± S) | 31.98 ± 4.37 | 34.56 ± 4.72 | 5.821 | 0.000 |
 Type of infertility |  |  | 13.272 | 0.000 |
  Primary infertility | 2600(54.74) | 212(45.89) |  |  |
  Secondary infertility | 2150(45.26) | 250(54.11) |  |  |
 Teratozoospermia | 175(3.68) | 20(4.33) | 0.486 | 0.486 |
 Sperm quality |  |  | 192.875 | 0.000 |
  Normal | 2840(59.79) | 136(29.44) |  |  |
  Mild or moderate asthenospermia | 1025(21.58) | 218(47.19) |  |  |
  Severe asthenospermia | 320(6.74) | 49(10.61) |  |  |
  Others | 565(11.89) | 59(12.76) |  |  |