Table 1.

Characteristics of the studies included in the meta-analysis

	Country	N		Patients’ age (years)	Treatment		Embryo stage	Outcome (rates)
		hCG group	Control group		hCG group	Control group
Mansour et al. [3]	Egypt	100 IU hCG: 83 200 IU hCG: 84 500 IU hCG: 107	Control 1: 93 Control 2: 105	≤ 40	100, 200, and 500 IU hCG in 0.04 ml culture medium 7 min before ET	No hCG or culture medium	Day 2 or 3, cleavage stage	Clinical pregnancy, implantation, miscarriage, delivery
Hong et al. [14]	New Jersey	148	1152	< 43	500 IU hCG (purified urinary) in 0.02 ml culture media less than 3 min before ET	0.02 ml culture media without hCG	Day 6, fresh or frozen, blastocyst stage	Sustained implantation, ongoing pregnancy
Zarei et al. [15]	Iran	84	98	18–40	rhCG 250 μg (0.5 ml), 12 min before ET	0.5 ml normal saline instead of hCG, 12 min before ET	Day 3, cleavage stage	Implantation, clinical pregnancy, ongoing pregnancy, abortion and ectopic pregnancy
Aaleyasin et al. [16]	Iran	240	243	< 40	500 IU hCG (urinary) in 0.05 ml culture media 5–7 min before ET	0.05 ml culture media without hCG	Day 2 or 3, cleavage stage	Implantation, clinical pregnancy, spontaneous, abortion, live birth rate
Wirleitner et al. [5]	Austria	Cohort A: 89 Cohort B: 510	Cohort A: 93 Cohort B: 494	≤ 43	500 IU hCG in 0.04 ml of culture media, cohort A infusion on Day 3 after ovum pick-up; cohort B infusion 3 min before ET	0.04 ml culture medium without hCG	Day 5, blastocyst, SET or DET	Pregnancy, clinical pregnancy, implantation, live birth rate, miscarriage
Navali et al. [8]	Iran	71	67	≤ 41	500 IU: 0.1 ml (500 IU hCG) and 0.4 ml normal saline were given via insulin syringe immediately after oocyte retrieval	0.5 ml normal saline instead of hCG	Day 3	Biochemical pregnancy, clinical pregnancy, implantation, ongoing pregnancy, abortion, ectopic pregnancy

hCG human chorionic gonadotropin, rhCG recombinant human chorionic gonadotropin, ET embryo transfer, SET single embryo transfer, DET double embryo transfer