With the advances in getting novel stimulation protocols, reproductive immunology, having facilities of embryo culture along with testing technologies, implantation continues to be the step which basically prevents the success in artificial reproductive technology (ART). Earlier we reviewed on how chronic endometritis has become a major factor in limiting implantation and how lot of advances have been achieved in diagnosis and treatment of chronic endometritis (CE) and steps that are being taken to optimize diagnosis and treatment of CE which is one step that might help in improving implantation [1]. Here we discuss another factor creating controversy regarding implantation concerning the role of endometrium thickness at the time of transfer of embryos. There has been no doubt that having the most thick endometrium has >relation with success in implantation at the time of in vitro fertilization (IVF) [2-5]. Almost all of us have had in mind that if the endometrium is thin it is not suitable for moving on to embryo transfer (ET). We presume at that stage that once ET has crossed 7 or 8mm that further results are on the basis of the embryo. Of these the latest study by Liu., et al. [2] documented a reduction in both clinical pregnancy along with live birth rates at a significant level for every mm decrease below 8mm in preovulatory phase in 24,000 fresh IVF-ET cycles. Similarly, in frozen thawed embryo transfer (FET) cycles with every mm decrease in Endometrial Thickness < 7 mm in > 20,000 FET cycles.

References

1. Kulvinder Kochar Kaur., et al. “Importance of Chronic Endometritis (CE) in RIF-An update on diagnosis and treatment”. OAJSRD 5 (2019).
2. Liu KE., et al. “The impact of a thin lining on fresh and frozen thaw IVF outcomes: an analysis of over 40, 000 embryo transfers”. Human Reproduction 10 (2018): 1883-1888.
3. Isaacs JD Jr., et al. “Endometrial Thickness is a valid monitoring parameter in cycles of ovulation induction with menotropins alone”. Fertility and Sterility 65 (1996): 262-266.
4. Weissman A., et al. “The detrimental effect of increased Endometrial Thickness on implantation and pregnancy rates and outcomes in an in vitro fertilization program”. Fertility and Sterility 1 (1999): 147-149.
5. Haas J., et al. “Endometrial compaction (decreased thickness) in response to progesterone results in optimal pregnancy outcome in frozen embryo transfers”. Fertility and Sterility 3 (2019): 503-509.
6. Labarta E., et al. “Low serum progesterone on the day of embryo transfer is associated with a diminished ongoing pregnancy rate inn oocyte donation cycles after artificial endometrial preparation: a prospective study”. Human Reproduction 12 (2017): 2437-2442.
7. Kofinas JD., et al. “Serum progesterone levels greater pregnancy than 20 ng/dl [sic]on day of embryo transfer is associated with lower live birth and higher pregnancy rates”. Journal of Assisted Reproduction and Genetics 9 (2015): 1395-1399.
8. Colombo S., et al. “Significance of endometrial lining decrease after progesterone start in synthetic frozen embryo transfer (FET) cycles”. Fertility and Sterility 5 (2017): e304-e305.
9. Kulvinder Kochar Kaur., et al. “Autologous Platelet rich plasma (PRP): A Possibility of becoming a revolutionary therapy in the field of Gynaecology and reproductive Endocrinology and Infertility-A Systematic Review”. Progress in Women's Health Care1 (2019): 1-13.
10. Forman EJ. “The receptive endometrium: the thinner the better?” Fertility and Sterility 3 (2019): 469-470.