Embryo Transfer with Suboptimal Endometrium

The condition of the endometrium (uterine lining) is crucial for the implantation of an embryo. Typically, the minimum endometrial thickness for a successful transfer is set at 7 millimeters.

For women whose endometrium is repeatedly thinner than this value, medication is often used to improve endometrial thickness.

However, it appears that the quality of the endometrium may be more important than its thickness. This can be well assessed via ultrasound (triple-layer pattern).
This raises the question: Is it worth performing an embryo transfer if the endometrial conditions seen on ultrasound are not optimal?

Yes, if certain conditions are met, according to the results of a retrospective study from Turkey (Kumbak B, Erden HF, Tosun S, Akbas H, Ulug U, Bahçeci M. Outcome of assisted reproduction treatment in patients with endometrial thickness less than 7 mm. Reprod Biomed Online. 2009 Jan;18(1):79-84).

The study analyzed 175 treatment cycles from the years 2000-2004, in which the endometrial thickness was less than 7 millimeters.

Pregnancy occurred in 30% of the cycles, but only 58% of these pregnancies were carried to term, resulting in a live birth rate of 17%. The number of miscarriages was higher than usual in the center.

The outcomes were significantly better in patients who:

• were younger than 35 years old
• retrieved more than 5 eggs
• had 3 or more embryos available for transfer

The study concluded that for a young woman with a normal response to hormone stimulation and a sufficient number of embryos, the transfer should be carried out even with a thinner endometrium.

Otherwise, it may be better to freeze the embryos and transfer them at a later time when the endometrial condition has improved.

For women whose endometrium remains suboptimal despite all efforts, transfer under less-than-ideal conditions is often the only option.