D6 blastocyst transfer on day 6 in frozen-thawed cycles should be avoided: a retrospective cohort study

Table 1 Comparison of FET cycles between the D6-on-D5 group and D6-on-D6 group

	D6-on-D5 group(n = 103)	D6-on-D6 group(n = 415)	P-value
Maternal age(years)	31.89 ± 4.46	31.96 ± 4.68	0.890
Paternal age (years)	33.88 ± 4.97	34.08 ± 5.25	0.726
BMI(kg/m²)	21.23 ± 2.67	21.27 ± 2.70	0.896
Endometrial thickness (mm)	9.82 ± 1.37	9.77 ± 1.40	0.746
Number of blastocysts transferred	1.39 ± 0.49	1.33 ± 0.47	0.278
Type of infertility
Primary infertility	41.7% (43)	48.4%(201)	0.224
Secondary infertility	58.3% (60)	51.6%(214)
Endometrial preparation
Natural cycles	38.8% (40)	38.8% (161)	0.994
HRT cycles	61.2% (63)	61.2% (254)
Number of blastocyst transferred
Single blastocyst transfer	61.2% (63)	67.0% (278)	0.265
Double blastocyst transfer	38.8% (40)	33.0% (137)
Quality of blastocyst transferred
Qualified	41.7% (43)	45.1% (187)	0.545
Good	58.3% (60)	54.9% (228)
Clinical pregnancy rate (%)	55.3(57/103)	37.3(155/415)	0.001
Implantation rate (%)	44.8(64/143)	32.6(180/552)	0.007
Early miscarriage rate (%)	21.1(12/57)	16.7(26/155)	0.471
Multiple pregnancy rate (%)	12.3(7/57)	16.1(25/155)	0.488

Data are presented as mean ± standard deviation (SD) or % (n )
BMI body mass index, HRT hormone replacement therapy, FET frozen-thawed embryo transfer, D6-on-D5 group cycles with blastocysts formed and cryopreserved on day 6 that were transferred on day 5, D6-on-D6 group cycles with blastocysts formed and cryopreserved on day 6 that were transferred on day 6

ISSN: 1471-2393