Assessment of Endometrial Thickness, Endometrial Pattern and Subendometrial Blood Flow for Evaluation of Endometrial Receptivity in Intracytoplasmic Sperm Injection

Abstract

Embryo implantation represents a critical step of the reproductive process and consists of a unique biological phenomenon. The blastocyst comes into intimate contact with the endometrium and forms the placenta that will provide an interface between the growing fetus and the maternal circulation (Guzeloglu-Kayisli et al., 2009). Successful implantation requires a receptive endometrium (Simon et al., 2000). The human endometrium undergoes a complex series of organized proliferative and secretory changes in each menstrual cycle and exhibits only a short period of receptivity, known as the ‘window of implantation’ (Strowitzki et al., 2006). Each month, the human endometrium undergoes a series of distinct cyclical changes in preparation to receive the developing blastocyst. Such changes necessitate well-controlled, dynamic remodelling of the endometrial microvasculature through the processes of angiogenesis and arteriogenesis (Smith, 2000; Rogers and Abberton, 2003). The standard method of endometrial dating is the histological evaluation of an endometrial biopsy (Noyes et al., 1950). Obviously, such an invasive method is not acceptable in order not to damage the endometrium. Therefore, endometrial receptivity should be ideally assessed before embryo transfer using a non-invasive method (Alcázar, 2006). Transvaginal ultrasonography may represent theoretically such an ideal non-invasive technique. Several sonographic parameters have been used to assess uterine receptivity, including endometrial thickness, endometrial pattern and endometrial subendometrial and uterine blood flow (Chien et al., 2004). However, many studies performed in the last 15 years clearly show that all of these sonographic parameters have a low predictive value for determining endometrial or uterine receptivity (Friedler et al., 1996). Therefore, the method to predict endometrial receptivity has yet to be established. However with the advent of Two-dimensional ultrasound it became possible to perform a reliable and reproducible sonographic endometrial volume calculations as well as an assessment of endometrial and subendometrial vascularization. Therefore, some researchers have evaluated the role of endometrial volume as well as subendometrial and endometrial vascularization for predicting uterine receptivity (Alcázar, 2006).