Association Between Pregnancy Outcomes and the Time of Progesterone Exposure of D6 Single-Blastocyst Transfer in Frozen-Thawed Cycles: A Retrospective Cohort Study

Figures & data

Figure 1 FET protocols.

Table 1 Patients Characteristics Between Group A and Group B

Parameters	Group A (n=1634)	Group B (n=395)	P
Age	31.33±3.88	31.06±3.70	0.205
BMI	23.87±3.79	23.88±3.65	0.972
AMH	3.76±3.10	3.90±3.10	0.439
Type of infertility
Primary	46.2% (755/1634)	50.9% (201/395)	0.094
Secondary	53.8% (879/1634)	49.1% (194/395)
Etiology of infertility
Female factors	74.6% (1219/1634)	72.7% (287/395)	0.274
Male factors	18.3% (299/1634)	17.5% (69/395)
Mixed	2.0% (33/1634)	3.3% (13/395)
Unexplained	5.1% (83/1634)	6.6% (26/395)
FSH	6.82±2.32	6.62±2.18	0.125
LH	5.60±3.87	5.52±3.71	0.702
E2	45.12±49.93	44.64±51.34	0.865
AFC	15.14±9.03	14.15±8.28	0.048*
No. of retrieved oocytes	10.35±6.10	10.51±6.25	0.649
No. of Excellent embryos	4.38±3.16	4.46±3.279	0.692
Fresh embryo transfer rate	42.8% (700/1634)	40.5% (160/395)	0.400

Note: *P<0.05.

Abbreviations: BMI, body mass index; AMH, anti-Müllerian hormone; FSH, follicle-stimulating hormone; LH, luteinizing hormone; E₂, estradiol; AFC, number of antral follicle count.

Table 2 Frozen-Embryo Transfer Cycles Parameters and Pregnancy Outcomes Between Group A and Group B

Parameters/Outcomes	Group A (n=1634)	Group B (n=395)	P
Endometrium preparation
NC	58.0% (947/1634)	55.2% (218/395)	0.009*
SC	5.8% (95/1634)	10.1% (40/395)
HRC	36.2% (592/1634)	34.7% (137/395)
Endometrial thickness	0.95±0.17	0.95±0.17	0.654
Blastocysts morphological grade
Excellent	16.3% (266/1634)	17.7% (70/395)	0.777
Average	58.9% (962/1634)	58.2% (230/395)
Poor	24.8% (406/1634)	24.1% (95/395)
Biochemical pregnancy rate	60.2% (984/1634)	53.2% (210/395)	0.011*
CPR	49.8% (814/1634)	47.1% (186/395)	0.330
Miscarriage rate	21.6% (176/814)	17.7% (33/186)	0.240
Preterm birth rate	6.8% (55/814)	8.6% (16/186)	0.377
LBR	38.7% (633/1634)	38.7% (153/395)	0.999

Note: *P<0.05.

Abbreviations: FET, Frozen-thawed embryo transfer; NC, natural cycle; SC, stimulated cycle; HRC, hormone replacement cycle; LBR, live birth rate; CPR, clinical pregnancy rate.

Table 3 Pregnancy Outcomes of the Subgroup Analysis Comparing Group A with Group B in NC, SC and HRC Respectively

Outcomes	Group A	Group B	P
Natural cycles	n=947	n=218
Biochemical pregnancy rate	59.2% (561/947)	56.4% (123/218)	0.446
CPR	50.5% (478/947)	48.6% (106/218)	0.622
Miscarriage rate	19.2% (92/478)	16.0% (17/106)	0.443
Preterm birth rate	5.2% (25/478)	11.3% (12/106)	0.020*
LBR	40.3% (382/947)	40.8% (89/218)	0.895
Stimulated cycles	n=95	n=40
Biochemical pregnancy rate	60.0% (57/95)	47.5% (19/40)	0.181
CPR	48.4% (46/95)	40.0% (16/40)	0.370
Miscarriage rate	26.1% (12/46)	18.8% (3/16)	0.555
Preterm birth rate	13.0% (6/46)	0.0% (0/16)	0.128
LBR	35.8% (34/95)	32.5% (13/218)	0.714
Hormone replacement cycles	n=592	n=137
Biochemical pregnancy rate	61.8% (366/592)	49.6% (68/137)	0.009*
CPR	49.0% (290/592)	46.7% (64/137)	0.632
Miscarriage rate	24.8% (72/290)	20.3% (13/64)	0.444
Preterm birth rate	8.3% (24/290)	6.3% (4/64)	0.587
LBR	36.7% (217/592)	37.2% (51/137)	0.901

Note: *P<0.05.

Abbreviations: NC, natural cycle; SC, stimulated cycle; HRC, hormone replacement cycle; LBR, live birth rate; CPR, clinical pregnancy rate.

Table 4 Multivariable Regression Analysis of Preterm Birth Rate

Preterm Birth Rate	cOR (95% CI)	P	aOR (95% CI)	P
The 7th day of progesterone exposure	2.313 (1.122–4.768)	0.023*	2.347 (1.129–4.877)	0.022*
Secondary infertility	2.375 (1.128–5.002)	0.023*	2.360 (1.115–4.996)	0.025*
BMI	1.087 (0.991–1.192)	0.076	1.084 (0.987–1.190)	0.091

Notes: *P<0.05. Potential confounders included time of transfer, type of infertility, BMI.

Abbreviations: BMI, body mass index, cOR, crude odds ratio, aOR, adjust odds ratio.

Table 5 Univariable Analysis of Patients (with No Preterm Birth or Preterm Birth)’ Basic Characteristics in Natural Cycles

Parameters	No Preterm Birth (n=547)	Preterm Birth (n=37)	P
The 7th day of progesterone exposure	17.2% (94/547)	32.4% (12/37)	0.020*
Age	31.35±3.74	31.95±3.61	0.338
BMI	23.42±3.30	24.44±4.19	0.155
AMH	3.19±2.33	3.33±2.30	0.721
Type of infertility
Primary	46.8% (256/547)	27.0% (10/37)	0.019*
Secondary	53.2% (291/547)	73.0% (27/37)
Etiology of infertility
Female factors	74.4% (396/547)	64.9% (24/37)	0.522
Male factors	20.1% (110/547)	27.0% (10/37)
Mixed	2.2% (12/547)	0.0% (0/37)
Unexplained	5.3% (29/547)	8.1% (3/37)
FSH	7.00±2.33	6.58±2.48	0.323
LH	5.27±3.36	5.26±3.56	0.978
E2	44.46±45.68	54.87±91.70	0.498
AFC	15.10±8.56	14.97±7.07	0.927
No. of retrieved oocytes	10.06±5.63	10.92±6.60	0.375
No. of Excellent embryos	4.38±3.12	4.76±3.48	0.476
Fresh embryo transfer	45.2% (247/547)	45.9% (17/37)	0.925
Endometrial thickness	1.00±0.17	1.01±0.18	0.579
Blastocysts morphological grade
Excellent	21.2% (116/547)	27.0% (10/37)	0.610
Average	60.5% (331/547)	59.5% (22/37)
Poor	18.3% (100/547)	13.5% (5/37)

Note: *P<0.05.

Abbreviations: BMI, body mass index; AMH, anti-Müllerian hormone; FSH, follicle-stimulating hormone; LH, luteinizing hormone; E₂, estradiol; AFC, number of antral follicle count.

Table 6 Characteristics of Patients with Excellent and Average Blastocyst Morphological Grades Between Group C and Group D

Parameters	Group C (n=1228)	Group D (n=300)	P
Age	31.22±3.91	30.97±3.67	0.306
BMI	23.85±3.81	23.94±3.76	0.708
AMH	3.79±3.04	3.94±3.11	0.453
Type of infertility
Primary	46.6% (572/1228)	51.0% (153/300)	0.169
Secondary	53.4% (656/1228)	49.0% (147/300)
Etiology of infertility
Female factors	74.1% (910/1228)	72.7% (218/300)	0.115
Male factors	19.1% (235/1228)	16.7% (50/300)
Mixed	1.9% (23/1228)	3.3% (10/300)
Unexplained	4.9% (60/1228)	7.3% (22/300)
FSH	6.85±2.66	6.76±3.51	0.607
LH	5.66±3.92	5.57±3.84	0.713
E2	45.52±45.25	46.20±57.95	0.589
AFC	15.09±8.80	14.26±8.46	0.140
No. of retrieved oocytes	10.56±6.09	10.55±6.33	0.973
No. of Excellent embryos	4.56±3.15	4.61±3.40	0.800
Fresh embryo transfer rate	45.8% (562/1228)	40.0% (120/299)	0.072

Abbreviations: BMI, body mass index; AMH, anti-Müllerian hormone; FSH, follicle-stimulating hormone; LH, luteinizing hormone; E₂, estradiol; AFC, number of antral follicle count.

Table 7 Frozen-Embryo Transfer Cycles Parameters and Pregnancy Outcomes Between Group C and Group D in Patients with Excellent and Average Blastocyst Morphological Grades

Parameters/Outcomes	Group C (n=1228)	Group D (n=300)	P
Endometrium preparation
NC	58.6% (719/1228)	55.3% (166/300)	0.094
SC	6.4% (79/1228)	10.0% (30/300)
HRC	35.0% (430/1228)	34.7% (103/300)
Endometrial thickness	0.97±0.17	0.96±0.17	0.549
Blastocysts morphological grade
Excellent	7.8% (96/1228)	10.7% (32/300)	0.110
Average	92.2% (1132/1228)	89.3% (268/300)
Biochemical pregnancy rate	63.4% (779/1228)	55.0% (165/300)	0.007*
CPR	54.2% (665/1228)	49.3% (148/300)	0.134
Miscarriage rate	20.0% (133/665)	16.2% (24/148)	0.292
Preterm birth rate	7.7% (51/665)	8.1% (12/148)	0.857
LBR	42.8% (526/1228)	41.0% (123/300)	0.565

Note: *P<0.05.

Abbreviations: FET, Frozen-thawed embryo transfer; NC, natural cycle; SC, stimulated cycle; HRC, hormone replacement cycle; LBR, live birth rate; CPR, clinical pregnancy rate.

Data Sharing Statement

The data used to support the findings of this study are included in the article. Also, if readers need detailed information, he/she can Email the corresponding author.