**1. Introduction**

398 Endometriosis - Basic Concepts and Current Research Trends

Yeh, J. & Seibel, MM. (1987). Artificial insemination with donor sperm: A review of 108

Yovich, JL.; Yovich, JM.; Tuvik, AI.; Matson, PL. & Willcox DL. (1985). In-vitro fertilization

patients. Obstet Gynecol, 70: 313–6.

for endometriosis. *Lancet*, 2(8454): 552.

Several reports have supported the concept of reduced fecundity in women with endometriosis (Garrido et al., 2002; 2000). Contradictory data have been reported for in vitro fertilization (IVF) outcomes in patients with endometriosis (Garrido et al., 2002; Garcia-Velasco & Arici, 1999; Kumbak et al., 2008; Fernando et al., 2008). Some studies suggest lower fertilization, implantation, and pregnancy rates in women with endometriosis (Barnhardt et al., 2002; Al-Fadhli et al., 2006), possibly owing to impaired oocyte quality with consequent poor embryo quality, or to endometrial defects or defective interactions between the endometrium and the embryo (Kumbak et al., 2008, Brizek et al., 1995; Pellicer et al., 1995).

Oocyte quality depends on proper cytoplasmic and nuclear maturation (Kim et al., 1998), with the latter requiring the presence of normal cell spindles that guide chromosome segregation during meiosis (Wang & Keefe, 2002; Mandelbaum et al., 2004; De Santis et al., 2005; Volarcik et al., 1998; Van Blerkom & Davis, 2001). The cell spindle of the oocyte is extremely sensitive to several factors, including oxidative stress (Liu et al., 2003; Navarro et al., 2004; 2006), which might be involved in the etiopathogenesis of infertility related to endometriosis (Campos Petean et al, 2008; Mansour et al, 2009; Jozwik et al., 1999; Carbone et al., 2003).

The oxidative balance of the reproductive female tract depends on some types of free radicals and on different antioxidant mechanisms that neutralize them. There are two major groups of free radicals: reactive oxygen species and reactive nitrogen species.
