INTRODUCTION

As described in textbooks and numerous scientific publications, human reproduction is a relatively inefficient process and this paradox is critical for the survival of the species (1, 2). The chance of achieving a spontaneous pregnancy after timed intercourse is about 30 percent. Moreover, up to 30 percent of early human embryos fail to develop into viable fetuses, and this is largely, but not exclusively, due to chromosomal abnormalities, implantation failure, and/or recurrent miscarriage (1–3). Scientists, clinicians, and pharmaceutical companies have tried for more than fifty years to develop methods, molecules, and protocols to improve fertility first in animal models but ultimately for couples with conception difficulties. Despite their efforts they have not yet found the ideal regimen, compounds, and/or protocols to achieve the maximum pregnancy rate expected by these infertile couples (4).

Infertility affects about 15 percent of couples of reproductive age, with infertility defined as one year of unprotected coitus without conception. Previously considered as a female problem, it is now widely accepted that the male factors represent between 40–50 percent of infertility. Female factors are recognized in 25–30 percent of infertile couples, whereas 10–15 percent will ultimately be classified as unexplained infertility (4). In Western countries, infertility is a growing problem; one of the causes is that increasingly couples decide to delay childbearing to an age where they have to deal with the problem of unintended infertility. This problem of life choice is now also emerging in countries like India and China.