Table 1.

Characteristics of 5208 participants at baseline.

Variables	All (N = 5208)	Non-pregnancy (N = 2368)	Pregnancy (N = 2840)	P -value
Age (years)a	31.00 (28.00, 34.00)	31.00 (28.00, 34.00)	31.00 (28.00, 33.00)	<0.001
BMI (kg/m2)a	21.77 (19.95, 24.03)	21.52 (19.81, 23.87)	21.88 (20.03, 24.14)	0.003
Endometrial thickness on hCG day (mm)a	10.50 (9.50, 12.00)	10.50 (9.50, 12.00)	10.50 (9.50, 12.00)	0.001
Total dose of Gn (IU)a	1950.00 (1575.00, 2475.00)	1950.00 (1575.00, 2475.00)	2000.00 (1575.00, 2475.00)	0.571
Duration of infertility (years)a	3.00 (1.00, 4.00)	3.00 (1.00, 5.00)	3.00 (1.00, 4.00)	0.144
Number of retrieved oocytesa	10.00 (7.00, 13.00)	9.00 (6.00, 13.00)	10.00 (7.00, 13.00)	<0.001
Number of embryo transfer, n (%)
Single	1735 (33.30)	829 (35.00)	906 (31.90)	0.019
Double	3473 (66.70)	1539 (65.00)	1934 (68.10)
Stage of embryo transfer, n (%)
Cleavage	3230 (62.00)	1525 (64.40)	1705 (60.00)	0.001
Blastocyst	1978 (38.00)	843 (35.60)	1135 (40.00)
Stimulation protocol, n (%)
GnRH antagonist	2321 (44.60)	1101 (46.50)	1220 (43.00)	0.036
GnRH agonist	2839 (54.50)	1247 (52.70)	1592 (56.10)
Other protocols	48 (0.90)	20 (0.80)	28 (1.00)
Infertility type, n (%)
Primary infertility	2471 (47.40)	1123 (47.40)	1348 (47.50)	0.999
Secondary infertility	2737 (52.60)	1245 (52.60)	1492 (52.50)
Cause of infertility, n (%)
Tubal factor	4761 (91.40)	2153 (90.90)	2608 (91.80)	0.263
Ovulation disorders	447 (8.60)	215 (9.10)	232 (8.20)
Year of embryo transfer, n (%)
2020	1600 (30.70)	714 (30.20)	886 (31.20)	0.365
2021	1798 (34.50)	837 (35.30)	961 (33.80)
2022	1640 (31.50)	732 (30.90)	908 (32.00)
2023	170 (3.30)	85 (3.60)	85 (3.00)

Abbreviations: Gn, gonadotropin.

^aCited as medians (interquartile range, IQR).