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Table 1 Basal demographic and cycle features of FETs which proceeded either within the immediate cycle following OPU (Immediate FET group) or subsequently (Delayed FET group) after a failed-fresh ET. Data are presented as numbers (%) unless otherwise noted

From: Immediate versus delayed frozen embryo transfer in women following a failed IVF-ET attempt: a multicenter randomized controlled trial

Characteristic Immediate FET group Delayed FET group P-value
Randomized subjects 366 366  
Female age at oocyte retrieval (years; mean (SD)) 33.8 (3.2) 33.3 (4.1) 0.062
Etiology of infertility    0.815
 Tubal factor 184 (50.3) 177 (48.4)  
 Anovulation 43 (11.7) 36 (9.8)  
 Male factor 59 (16.1) 63 (17.2)  
 Combined factor 68 (18.6) 75 (20.5)  
 Unexplained sterility 12 (3.3) 15 (4.1)  
FET interval (days; mean (SD)) 25.2 (5.4) 103.5 (23.3) 0.001
Duration of infertility (years; median (IQR)) 4 (4) 5 (2) 0.817
Nulliparous 176 (48.1) 180 (49.2) 0.767
Gravidity (median (IQR)) 1 (2) 1 (2) 0.978
Parity (median (IQR)) 0 (1) 0 (1) 0.844
BMI (kg/m2; mean (SD)) 23.1 (2.9) 23.5 (2.9) 0.116
AMH (ng/ml; median (IQR)) 2.9 (1.6) 3.1 (1.2) 0.354
Basic FSH (mIU/ml; mean (SD)) 6.7 (1.0) 6.8 (1.9) 0.920
Basic LH (mIU/ml; mean (SD)) 5.0 (1.5) 5.0 (1.2) 0.688
Basic estradiol (pg/ml; median (IQR)) 35.4 (7.0) 35.3 (8.4) 0.755
Total AFC (mean (SD)) 10.4 (3.2) 10.7 (2.9) 0.329
No of days of COS (mean (SD)) 10.7 (2.1) 10.9 (1.8) 0.132
Total Gn dose administered (IU; mean (SD)) 2140.5 (469.3) 2180.5 (551.2) 0.291
Method of fertilization    0.875
 IVF 247 (67.5) 245 (66.9)  
 ICSI 119 (32.5) 121 (33.1)  
No of oocytes retrieved (mean (SD)) 10.5 (2.1) 10.7 (2.8) 0.170
No of embryos available for transfer (median (IQR)) 5.5 (2) 5 (5) 0.235
No of high-quality day 3 embryos (median (IQR)) 2 (0) 2 (2) 0.315
No of embryos transferred in fresh ET cycle (median (IQR)) 2 (0) 2 (0) 0.697
 Single embryo transfer 31 (8.5) 34 (9.3)  
 Double embryo transfer 335 (91.5) 332 (90.7)  
No of frozen thawed embryos transferred (median (IQR)) 2 (0) 2 (0) 0.956
 Single embryo transfer 32 (9.8) 31 (9.7)  
 Double embryo transfer 294 (90.2) 289 (90.3)  
Endometrial thickness prior to FET (mm; mean (SD)) 10.5 (1.8) 10.3 (1.9) 0.388
Moderate/severe depression prior to FET (MDI) a 20/326 (6.1) 34/320 (10.6) 0.039
High stress level prior to FET (PSS) b 73/326 (22.4) 97/320 (30.3) 0.022
  1. Abbreviation: FET Frozen embryo transfer, IQR Interquartile range, OPU Ovum pick-up, Interval Days elapsed from oocyte retrieval to frozen embryo transfer, BMI Body mass index, AMH Anti-müllerian hormone, FSH Follicle stimulating hormone, LH Luteinizing hormone, AFC Antral follicle count, COS Controlled ovarian stimulation, IVF In-vitro fertilization, ICSI Intracytoplasmic sperm injection, Gn Gonadotropin, IU International units, MDI Major Depression Index, PSS Cohen’s Perceived Stress Scale
  2. a Moderate depression (two core symptoms and four or more additional symptoms); Severe depression (three core symptoms and five or more additional symptoms)
  3. b High stress level defined as ≥ 19 on the PSS scale