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Table 1 Baseline characteristics of the two cohorts in fresh ET and FET cycles

From: Neonatal outcomes of singleton live births with vanishing twin syndrome following double embryos transfer in assisted reproductive technology: a retrospective cohort study

  Fresh cycles Frozen cycles
Study
group
N = 1196
Control group
N = 1576
P value t/x2 value Study
group
N = 1275
Control group
N = 2173
P value t/x2 value
Age 29.5 ± 3.9 29.8 ± 4.2 0.031* −2.16 30.7 ± 4.9 30.2 ± 4.8 0.001* 3.20
<35 1094 (91.5) 1406 (89.2) 0.061 3.47 913 (71.6) 1586 (73.0) 0.698 0.70
≥35 102 (8.5) 117 (10.8)    362 (28.4) 587 (27.0)   
BMI 22.9 ± 3.0 23.0 ± 3.1 0.15 −1.45 23.0 ± 2.5 22.8 ± 2.3 0.016* 2.42
Infertile year 1.8 ± 1.3 1.8 ± 1.8 0.86 0.18 2.5 ± 1.5 2.7 ± 1.5 0.001* 3.23
Cause of infertility    0.314 1.01    0.177 0.82
Tubal factor 788 (65.9) 1067 (67.7)    826 (64.8) 1458 (67.1)   
Male factor 408 (34.1) 509 (32.3)    449 (35.2) 715 (32.9)   
Current cycle 1.4 ± 0.7 1.4 ± 1.1 0.96 0.055 2.4 ± 1.8 2.4 ± 1.6 0.194 1.30
bFSH 7.0 ± 2.2 7.0 ± 3.7 0.84 −0.21 7.9 ± 2.6 7.7 ± 1.8 0.057 1.91
bE2 37.1 ± 8.9 36.5 ± 9.1 0.101 1.64 48.7 ± 16.0 49.5 ± 12.4 0.146 −1.45
bLH 4.6 ± 3.3 4.3 ± 2.8 0.21 1.82 4.4 ± 2.5 4.3 ± 2.1 0.201 1.28
PRL 414.7 ± 178.8 402.0 ± 204.8 0.089 1.703 4.9.3 ± 254.9 409.9 ± 184.8 0.939 −0.077
AMH 5.4 ± 0.60 5.3 ± 0.67 0.029* 0.089 5.1 ± 2.6 5.3 ± 2.8 0.068 −1.824
AFC 15.7 ± 4.4 15.5 ± 5.4 0.55 0.60 / / / /
Number of oocytes retrieved 10.5 ± 4.5 10.6 ± 3.9 0.53 0.62 / / / /
Number of available embryos 8.2 ± 1.2 8.0 ± 1.6 0.01* 2.57 / / / /
Number of high-quality embryos 5.1 ± 2.6 4.8 ± 2.4 0.003* 2.95 / / / /
embryo stage    0.000* 126.4    0.01* 6.57
cleavage-stage embryo 1015 (84.9) 1040 (66.0)    874 (68.5) 1395 (64.2)   
blastocyst 181 (15.1) 536 (34.0)    401 (31.4) 778 (35.8)   
endometrial thickness at the day of transplantation 11.6 ± 1.3 11.7 ± 1.1 0.002* −3.1 10.3 ± 1.9 10.2 ± 1.5 0.091 1.69
mode of delivery    0.000* 67.0    0.000* 210.9
cesarean section 766 (64.0) 1233 (78.2)    851 (66.7) 1899 (87.4)   
vaginal delivery 430 (36.0) 343 (21.8)    424 (33.3) 274 (12.6)   
  1. *p < 0.05 was statistically significant