Table 1.

Clinical outcomes of the 3 age groups.

	≤35 years (average age 29.92 years)	36–37 years (average age 36.44 years)	≥38 years (average age 40.36 years)	P value
Embryo transfer cycles	5963	475	571
Cause of infertility				<.05
Tubal	4054 (68.0%)	324 (68.2%)	385 (67.4%)
Endometriosis	254 (4.3%)	21 (4.4%)	11 (1.9%)
Ovulatory disorder	285 (4.8%)	6 (1.3%)	5 (0.9%)
Decline in ovarian reserve	202 (3.4%)	32 (6.7%)	89 (15.6%)
Male factor	1023 (17.2%)	55 (11.6%)	63 (11.0%)
Unexplained	855 (14.3%)	37 (7.8%)	18 (3.2%)
E2 on the day of FET	481.84	491.41	515.97	>.05
P on the day of FET	24.29	23.84	21.62	.024
Duration of infertility (yr)	3.7 ± 0.1	5.9 ± 0.5	7.7 ± 0.8	<.001
No. thawed embryo	11,054	909	1093
No. survived embryo	10,756	888	1064
Embryo survival rate	10,756 (97.3%)	888 (97.7%)	1064 (97.3%)	>.05
Endometrium preparation
HRT	5181 (86.9%)	437 (92.0%)	547 (95.8)	<.001
NC	124 (2.1%)	5 (1.1%)	2 (0.4%)
HMG	658 (11.0%)	33 (6.9%)	22 (3.8%)
No. high-quality embryo transfer	9096 (76.3%)	718 (75.6%)	825 (72.2%)	.01
Endometrium thickness (mm)	9.4 ± 0.0	9.3 ± 0.1	9.1 ± 0.1	.001
Pregnancy rate per cycle	4003 (67.1%)	254 (53.5%)	222 (38.9%)	<.001
Implantation rate per cycle	5449 (45.7%)	327 (34.4%)	272 (28.9%)	<.001
Live birth rate per cycle	3554/5963 (59.6%)	229/475 (48.2%)	190/571 (33.3%)	<.001
Multi pregnancy rate (%)	1250/3554 (35.2%)	62/229 (27.1%)	36/190 (18.9%)	<.001
Gestational days (d)	263.7 ± 0.8	263.5 ± 2.8	265.3 ± 4.0	.929
Neonatal weight (g)	3007.2 ± 14.3	3137.6 ± 66.9	3196.9 ± 72.4	.005
Preterm birth (<37 wks)	456/3554 (12.8%)	31/229 (13.5%)	29/190 (15.3%)	.604

E2 = estradiol, FET = frozen-thawed embryo transfers, HMG = human menopausal gonadotropin, HRT = hormone replacement therapy, NC = natural cycle, P = progesterone.