Table 5.

Comparisons of demographic and clinical characteristics between subgroups of the day 3 ET group

Parametera	Serum P levels (ng/ml), day 3 ETb
	<1.0	1.0-1.49	≥1.5
No. of fresh cycles	7627	2373	846
Female age (years)	31.1 ± 5.1	31.8 ± 5.0*	32.1 ± 5.1
BMI (kg/m2)	22.7 ± 3.2	22.3 ± 3.0*	22.1 ± 3.0
Basal FSH (IU/L)	7.7 ± 2.9	7.3 ± 2.4*	7.2 ± 2.2
Total dose of Gn (IU)	2201.2 ± 940.7	2268.6 ± 879.3*	2357.1 ± 890.1*
Serum E2 (pg/ml), hCG day	3941.8 ± 2118.6	5321.0 ± 2353.8*	6201.8 ± 4598.0*
Serum LH (IU/L), hCG day	2.0 ± 1.3	1.9 ± 1.4	1.72 ± 1.9*
Endometrial thickness (mm), hCG day	12.3 ± 2.4	12.2 ± 2.5	12.0 ± 2.4*
No. of oocytes retrieved	9.3 ± 4.4	11.1 ± 4.6*	12.0 ± 4.8*
No. of 2PN oocytes	6.4 ± 3.3	7.5 ± 3.5*	7.8 ± 4.8
No. of 2PN cleavage embryos	6.4 ± 3.3	7.5 ± 3.5*	7.8 ± 4.8
No. of available embryos	5.0 ± 2.8	5.7 ± 3.0*	5.9 ± 3.2
Fertilization rate (%)	69	67.4*	65.1*
Cleavage rate (%)	97.8	97.7	97.3**
No. of transferred embryos	2.10 ± 0.34	2.12 ± 0.34*	2.14 ± 0.39
No. of transferred top-quality embryos	1.97 ± 0.55	2.00 ± 0.53**	2.02 ± 0.56*
Implantation rate (%)	36.3	31.6*	26*
CPR (%)	50.4	45.5*	36.2*

Note: Day 3 ET subgroups according progesterone cut-off levels: <1 ng/ml, 1–1.49 ng/ml, and ≥1.5 ng/ml. P = progesterone

^aAll values are presented as the mean ± SD or count (%)

^bDifferences between subgroups were determined using ANOVA followed by the LSD-t test or the Kruskal-Wallis (KW) test and subsequent pairwise multiple comparisons for continuous variables and the chi-square test or Fisher’s exact test for categorical variables

*p < 0.01 compared with the previous subgroup

**p < 0.05 compared with the previous subgroup