To review the etiology, diagnosis and clinical importance of thin endometrium during assisted reproductive technology cycles and to find out better ways to deal with it. Precise and specific endometrial maturational development is crucial in allowing implantation following assisted reproduction. As endometrial biopsy is invasive and hormonal milieu assessment inaccurate, the need to evaluate endometrial development encouraged the use of high-resolution ultrasonography as an alternative non-invasive method of assessment for uterine receptivity. Ultrasonographic endometrial thickness measurement, endometrial pattern investigation, endometrial volume computation, uterine and subendometrial blood flow analysis by Doppler sonography are just some of the methods that we can utilize to have an idea of uterine receptivity and consequently to better predict pregnancy outcome following assisted reproductive technology cycles. There is a lot of debate on the administration of low-dose aspirin, estrogen, vaginal sildenafil citrate, pentoxifylline, vitamin E, and gonadotropin-releasing hormone agonist for the management of thin endometrium with an aim to increase the pregnancy and implantation rates in assisted reproductive technology cycles. Various recent modalities proposed for the treatment of thin endometrium seem to be useless and inefficient from an evidence-based medicine point of view. At the moment, evaluation of endometrium using different ultrasonographic markers seems to be superior to all those therapies.

Obesity is a worldwide problem. The effect of obesity on the outcome of assisted reproductive techniques is quite controversial. Although there is not an absolute consensus based on evidence, obesity may lengthen the duration of ovulation induction, increase the gonadotrophin dose, decrease the peak estradiol levels, number of mature follicles and number of oocytes retrieved, and increase the cycle cancellation rate. Moreover, obesity may have a negative impact on oocyte and embryo quality. Thus, fertilization, embryo transfer, implantation and pregnancy rates have been usually found to be low in many studies. In addition, oocyte retrieval and embryo transfer procedures can be difficult due to obesity itself. Finally, miscarriage rate is found to be high. None of the studies related with obesity and assisted reproduction has been designed as a randomized controlled trial, yet. Definition of obesity, cause of infertility, protocols used for ovulation induction, starting dose for gonadotrophins, oocyte and embryo-grading systems are not standardized among the studies. Some confounding factors, such as polycystic ovary syndrome status and age, are not taken into consideration. Obesity has a negative impact on the outcomes of assisted reproductive techniques.