Impact of having surplus blastocysts cryopreserved on the ongoing pregnancy rate following a fresh transfer

Figures & data

Table 1. Patients’ characteristics grouped according to whether they have surplus vitrified blastocysts in fresh embryo transfer cycle.

	Group A (1,731)	Group B (751)	p value
Female age (years)	31.6 (4.5)	34.7 (5.6)	<.001
BMI (kg/m^2)	23.36 (3.34)	23.31(3.32)	.673
AMH (ng/mL)	3.59 (2.30)	2.31 (1.89)	<.001
Infertility duration (years)	3.65 (3.29)	4.01 (3.89)	.025
OPU cycles, n (%)
1	1,426 (82.4)	460 (61.3)
>1	305 (17.6)	291 (38.7)
Diagnosis
Decreased ovarian reserve	22 (31.4)	48 (68.6)
Tubal factor	668 (74.9)	224 (25.1)
Ovulation disorder	15 (62.5)	9 (37.5)
Endometriosis	10 (45.5)	12 (54.5)
Male factor	435 (74.2)	151 (25.8)
Combined factors	204 (55.3)	165 (44.7)
Unexplained	377 (72.6)	142 (27.4)
Stimulation protocol, n (%)
GnRH ultra-long	1,167 (67.4)	306 (40.7)
GnRH antagonist	380 (22)	327 (43.5)
Others	184 (10.6)	118 (15.8)
Number of aspirated oocytes	11.4 (4.5)	6.1 (3.8)	<.001
Method of fertilization, n (%)
IVF	1,470 (84.9)	597 (79.5)
ICSI	261 (15.1)	154 (20.5)
Endometrial thickness (mm)	11.1 (2.9)	10.6 (2.8)
Number of embryos transferred	1.99 (0.18)	1.90 (0.47)	<.001
Transferred embryo stage
Cleavage stage	1,588 (91.7)	714 (95.1)
Blastula stage	143 (8.3)	37 (4.9)
Positive hCG, n (%)	1 128 (65.2)	308 (42.1)	<.001
Clinical pregnancy, n (%)	1,021 (59.0)	256 (34.1)	<.001
Miscarriage, n (%)	110 (10.8)	43 (16.8)	.008
Ongoing pregnancy, n (%)	899 (51.9)	209 (27.8)	<.001

Group A, fresh transfer cycle with a surplus of vitrified blastocysts; Group B, fresh transfer cycle with no surplus of vitrified blastocysts.

AMH, anti-Mullerian hormone; BMI, body mass index; OPU, ovum pick-up; GnRH-a, gonadotropin-releasing hormone analogue.

Continuous data are shown as the median (standard error) and were analyzed using one-way Anova.

Categorial variables are shown as number (percentage) and were analyzed using the chi-square test.

Table 2. Comparison of clinical outcomes between group A and B when retrieved 6 ∼ 15 oocytes in subgroups by female age.

	Subgroups of female age < 35 years					Subgroups of female age ≥ 35 years
	Group A (n = 950)	Group B (n = 226)	Relative risk	95% CI	p value	Group A (n = 312)	Group B (n = 128)	Relative risk	95% CI	p value
Positive hCG	652 (68.6)	127 (56.2)	1.22	1.08–1.38	<.001	171 (54.8)	48 (37.5)	1.46	1.14–1.87	.001
Clinical pregnancy	589 (62)	112 (49.6)	1.25	1.09–1.44	.001	150 (48.1)	40 (31.2)	1.54	1.16–2.04	.001
Miscarriage	49 (8.3)	14 (12.5)	0.67	0.38–1.16	.156	36 (24)	6 (15)	1.60	0.73–3.53	.223
Ongoing pregnancy	533 (56.1)	98 (43.4)	1.29	1.10–1.52	.001	112 (35.9)	32 (25)	1.44	1.03–2.01	.027

Group A, fresh transfer cycle with a surplus of vitrified blastocysts; Group B, fresh transfer cycle with no surplus of vitrified blastocysts.

Data presented as n (%).CI, confidence interval.

Table 3. Comparison of clinical outcomes between group A and B after transferring two day 3 embryos.

	Subgroup of two good-quality embryos transferred					Subgroup of two embryos transferred ,one of which is of good quality
	Group A (n = 1,368)	Group B (n = 220)	Relative risk	95%CI	p value	Group A (n = 158)	Group B (n = 132)	Relative risk	95%CI	p value
Positive hCG	899 (65.7)	116 (52.7)	1.25	1.09–1.42	<0.001	94 (59.5)	62 (47)	1.27	1.01–1.58	0.033
Clinical pregnancy	810 (59.2)	99 (45)	1.32	1.13–1.53	<0.001	86 (54.4)	55 (41.7)	1.31	1.02–1.67	0.030
Miscarriage	86 (10.6)	12 (12.1)	0.88	0.50–1.54	0.649	8 (9.3)	8 (14.5)	0.64	0.26–1.6	0.338
Ongoing pregnancy	718 (52.5)	87 (39.5)	1.33	1.12–1.58	<0.001	77 (48.7)	46 (34.8)	1.40	1.05–1.86	0.017

Group A, fresh transfer cycle with a surplus of vitrified blastocysts; Group B, fresh transfer cycle with no surplus of vitrified blastocysts.

Data presented as n (%).

Table 4. Multivariable logistic regression analysis of potential factors affecting ongoing pregnancy.

Variables	OR	95% CI	Adjusted p value
OPU cycles
1	Reference
>1	0.79	0.64 ∼ 0.98	0.034
Female age (years)
<30	Reference
30–34	0.96	0.78–1.17	0.672
35–39	0.63	0.49–0.80	<0.001
39	0.11	0.07–0.19	<0.001
Number of aspirated oocytes	1.02	1.00–1.04	0.03
Surplus vitrified blastocyst
No	Reference
Yes	1.52	1.21–1.92	<0.001
Number of good-quality embryos transferred
0	Reference
1	1.96	1.42–2.71	<0.001
2	2.00	1.50–2.68	<0.001

OR, odds ratio; CI, confidence interval.