Correcting an out-of-sync endometrium increases pregnancy rates

This study looks at the effect of adjusting the length of hormone treatment on pregnancy rates in women with an out-of-sync endometrium. 

Recent advances in fertility treatment have enabled women to freeze embryos (eggs fertilized with the male sperm prior to freezing) for future use. Reasons for freezing embryos include rapidly declining ovarian function, a diagnosis of cancer, or delaying child-bearing for other personal reasons.

Once thawed, the embryo has to implant successfully on the endometrium (the lining of the uterus or womb) for pregnancy to occur. However, there is a precise “window of implantation”, when the endometrium is ready to accept the embryo. Doctors can predict when this window occurs based on the day of ovulation (the day the egg is released from the ovaries). However, predicting this can be tricky, especially for women who have an “out-of-sync” endometrium. This may result in implantation at the wrong time and failed embryo transfer. 

This article aimed to suggest a more accurate way for doctors to accurately time implantation.

80 women who had a previous failed embryo transfer took part in this study. A trial cycle was performed in which hormones were administered to thicken the endometrium. Additionally, a simple endometrial-dating test was performed (a sample of endometrial tissue was surgically removed and inspected to determine if the endometrium was in-sync). Women with an out-of-sync endometrium received an adjusted hormone treatment prior to the real cycle, in which an embryo was transferred.

The authors found that 55 of the women had a normal “in-sync” endometrium, while 29 women had an “out-of-sync” endometrium. Most patients were out-of-sync by 2 days (some were up to 5 days). Adjusting the duration of hormone treated in the out-of-sync group led to improved implantation and pregnancy rates. The pregnancy rate in the out-of-sync group was 36.4%. This was just as good, if not better, than the in-sync group with a pregnancy rate of 23%. 

The authors concluded that, for women with out-of-sync endometrium, simple endometrial dating and hormone adjustment can improve pregnancy rates in frozen embryo transfer cycles. 

The authors did not compare the pregnancy rates in out-of-sync patients that did not receive hormonal adjustment.