Table 1 Material and cycle characteristics between the two groups
From: Fresh versus frozen embryo transfer for full-term singleton birth: a retrospective cohort study
|  | Fresh-ET (N = 2059) | FET(N = 2053) | Z/χ2 | P value |
|---|---|---|---|---|
Age | 29.4 ± 4.3 | 29.8 ± 4.2 | −3.230 | 0.001 |
BMI | 22.4 ± 3.0 | 23.3 ± 3.9 | −6.252 | 0.000 |
Infertile years | 3.6 ± 2.7 | 3.6 ± 2.8 | −0.135 | 0.893 |
Infertile type | Â | Â | 0.157 | 0.692 |
 Primary infertile | 1189 (57.7) | 1173 (57.1) |  |  |
 Secondary infertile | 870 (42.3) | 880 (42.9) |  |  |
Diagnosis of Infertile | Â | Â | 1.590 | 0.662 |
 Tube factor | 975 (47.4) | 982 (47.8) |  |  |
 Male factor | 505 (24.5) | 503 (24.5) |  |  |
 Male+female | 351 (17.0) | 364 (17.7) |  |  |
 Other/unknown | 228 (11.1) | 204 (9.9) |  |  |
No. of embryos transfer | 1.9 ± 0.4 | 1.9 ± 0.6 | −2.165 | 0.030 |
Embryo stage | Â | Â | 373.62 | 0.000 |
 D3 | 1855 (90.1) | 1333 (64.9) |  |  |
 D5 | 204 (9.9) | 720 (35.1) |  |  |
Delivery mode | Â | Â | 86.116 | 0.000 |
 Vaginal | 545 (26.5) | 303 (14.8) |  |  |
 Caesarean | 1514 (73.5) | 1750 (85.2) |  |  |
Gestational weeks | 39.0 ± 1.0 | 39.0 ± 1.1 | −2.791 | 0.005 |
Offspring sex | Â | Â | 0.524 | 0.469 |
 Male | 1077 (52.3) | 1097 (53.4) |  |  |
 Female | 982 (47.7) | 956 (46.6) |  |  |