Table 4.

Human sperm penetration into the ZP of unfertilised and fertilised oocytes

	Unfertilised oocytes		Fertilised oocytes
Experiment	Number of embedded spermatozoa per ZP mean ± SEM	Penetrated zona pellucida %	Number of embedded spermatozoa per ZP mean ± SEM	Penetrated zona pellucida %
1	0.93 ± 0.32	57 (8/14)a	0.18 ± 0.13**	18* (2/11)
2	1.14 ± 0.60	57 (4/7)	0.22 ± 0.11**	17*(4/23)
3	1.14 ± 0.43	57 (8/14)	0.26 ± 0.13**	21*(4/19)
Total	1.06 ± 0.23	57 (20/35)	0.23 ± 0.07***	19*** (10/53)

()^anumber of oocytes with penetrated zona pellucida/total number of oocytes; *,**,*** statistically different from unfertilised oocytes: * p < 0.05; ** p < 0.01; *** p < 0.001 with Student's t test (mean ± SEM) or Chi-squared test (%).