Table 2.

Pregnancy and birth outcomes compared between the immediate and delayed FET groups. Data are presented as numbers (%)

	Intention-to-treat analysis				Per-protocol analysis
	Immediate FET group	Delayed FET group	Relative risk (95% CI)	P-value	Immediate FET group	Delayed FET group	Relative risk (95% CI)	P-value
Subjects	366	366			326	320
Positive pregnancy	155 (42.3)	159 (43.4)	0.98 (0.83 to 1.15)	0.765	154 (47.2)	157 (49.1)	0.96 (0.82 to 1.13)	0.643
Embryo implantation	157/620 (25.3)	125/609 (20.5)	1.23 (1.00 to 1.52)	0.046	156/620 (25.2)	123/609 (20.2)	1.25 (1.01 to 1.53)	0.038
Clinical pregnancy a	137 (37.4)	111 (30.3)	1.23 (1.01 to 1.51)	0.042	136 (41.7)	109 (34.1)	1.23 (1.00 to 1.50)	0.045
Biochemical pregnancy loss	18 (11.6)	48 (30.2)	0.39 (0.24 to 0.63)	< 0.001	18 (11.7)	48 (30.6)	0.28 (0.23 to 0.63)	< 0.001
Clinical pregnancy loss b	15 (10.9)	13 (11.7)	0.94 (0.47 to 1.88)	0.850	15 (11.0)	12 (11.0)	1.00 (0.49 to 2.05)	0.996
Total pregnancy loss	33 (21.3)	61 (38.4)	0.56 (0.39 to 0.80)	0.001	33 (21.4)	60 (38.2)	0.56 (0.39 to 0.81)	0.001
Ectopic pregnancy	2 (1.3)	5 (3.1)	0.41 (0.08 to 2.08)	0.448	2 (1.3)	5 (3.2)	0.40 (0.08 to 2.04)	0.448
Multiple pregnancy	18 (13.1)	14 (12.6)	1.04 (0.54 to 2.00)	0.902	18 (13.2)	14 (12.8)	1.03 (0.54 to 1.98)	0.928
Ongoing pregnancy	122 (33.3)	98 (26.8)	1.25 (0.99 to 1.56)	0.053	121 (37.1)	97 (30.3)	1.22 (0.99 to 1.52)	0.067
Live birth	120 (32.8)	96 (26.2)	1.25 (0.99 to 1.57)	0.052	119 (36.5)	96 (30.0)	1.22 (0.98 to 1.52)	0.079

Abbreviation: FET Frozen thawed embryo transfer, CI Confidence interval

^a In the Immediate FET group, one woman conceived naturally and delivered a healthy male infant vaginally

^b In the Delayed FET group, two women conceived spontaneously, however, one miscarried in the second trimester because of fetal anomalies