The endometrium undergoes cyclic change during the menstrual cycle. In the follicular phase, elevated estrogen levels due to follicular growth leads to proliferative endometrial changes. Ovulation induces formation of corpus luteum which produces progesterone and elevated progesterone levels causes secretory changes in the endometrium. These hormone- driven endometrial changes provided optimal implantation conditions (Achache et al., 2006).
Evaluation of endometrial development and receptivity continues to be a challenge in reproductive medicine. Endometrial development and receptivity cannot be predicted using serum hormone levels, and methods such as histologic and molecular studies are not practical .(Esmalizadeh et al., 2007). Ultrasound examination is generally used for evaluation of the edometrium (Chien et al., 2002). Transvaginal ultrasound may be ideal tool for examining endometrial receptivity. Several sonographic parameters have been used to assess uterine receptivity, including endometrial thickness, volume, pattern, junctional zone contraction; endometrial, subendometrial, and uterine blood flow (Zaidi et al., 1995; Alcazar, 2006).
Recently, three- dimensional ultrasound (3D US) has become available (Pretorius, et al., 2001). In this technology any desired plane through an organ can be obtained , and a volume of a region of interest (ROI) can be acquired and stored. This volume can be further analysed in several ways such as navigation, multiplanar display, and surface rendering or volume calculation. This technique also allows a whole assessment of the endometrial and subendometrial vascularization (Raine – Fenning et al.,