With IVF and ICSI, 60% of oocytes fertilize and cleave normally over the first 48 hours. Good fertilization rates are expected in cases of abnormal sperm and low sperm count, For women younger than 35 years of age, the clinical pregnancy rate (fetal heart positive at 6 weeks gestation) for transfer of one fresh 5-day-old embryo is approximately 50-60%. Multiple pregnancy is more frequent if three or more cleavagestage embryos or blastocysts are transferred. A number of other factors influence the results of treatment, including embryo quality and particularly female age. Implantation and pregnancy rates decrease and pregnancy losses increase after age 35, mostly due to increasing abnormalities in the oocytes. For women aged 36 to 39 years, the live birth rate is about 70% of that for women younger than 36. For those 40 years and older using their own oocytes, the rate is about 30% that for women younger than 36.