Figure 3: Graphs representing the analysis of embryo quality versus pregnancy using Fisher’s exact test (fig A). Thirty-two embryos of Grades I and II (good quality) resulted in pregnancy, while 40 embryos – 17 in Grades I and II and 23 in Grades III and IV (poor quality) – did not result in pregnancy. Concerning the level of histones in sperm chromatin, 22 transferred embryos (10 of good and 12 of poor quality) had high histone levels (> 1%) and 50 (39 good and 11 poor quality embryos) had low histone levels (<0.99%).