Endometrial Preparation for Embryo Transfer

Dr. Preeti Moond
Fellow Infertility Specialist
Institute of Human Reproduction

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Endometrium is the inner dynamic lining of the uterus (womb) where a baby develops. Each month under the influence of hormones like Estrogen and Progesterone, the endometrium prepares itself for the implantation of an embryo.

How to prepare endometrium for Embryo transfer?

Endometrial preparation is just like preparing fertile soil for the sowing of good quality seeds. This is usually done in cases of oocyte donation, embryo donation and frozen embryo transfer (FET) cases. The thickness of the uterine (endometrial) lining is a useful predictor of implantation of embryo and pregnancy success. A thin endometrium can interfere with the process of implantation and it may be a rate-limiting factor for successful IVF. You can know more about the success rate of IVF in the linked article

What is the recommended endometrial lining thickness for Embryo Transfer?

For successful implantation of an embryo endometrial lining should have:

1. Thickness of at least 7mm (though successful pregnancy and delivery with as low as 4mm is also reported)
2. Multilayered ( triple line ) pattern
   Thickness and pattern of the endometrium is assessed by doing TVS (Transvaginal Sonography). Read more about Ultrasound and TVS here

3. Good endometrial blood flow for proper oxygenation (assessed by looking at the blood flow in the blood vessels supplying the uterus i.e uterine artery Doppler).
4. Endometrial volume (assessed by 3D vaginal sonography (TVS))
5. Activation and inactivation of genes, assessed by ERA. Click the linked article to know more about Endometrial Receptivity Assay (ERA)

What is the best method to prepare endometrium for embryo transfer?

There are multiple ways by which endometrial lining can be prepared. In normal ovulating women ovaries can be stimulated to use the natural hormones produced in the ovary i.e Stimulated Cycle Endometrial preparation.

In some women with decreased ovarian reserve, when aged more than 35 years, endometrial preparation is carried out by giving estrogen hormone starting from the day2 / day3 of menstruation after doing the baseline TVS (vaginal ultrasound). Estrogen is usually given in oral and/or topical (application on the skin) form approximately around the 9th day from the start of treatment TVS (vaginal ultrasound) and blood estrogen level is measured. If the thickness is lower than expected (Thin Endometrium) or blood estrogen level is less, the possibility of increasing the dose of estrogen and addition of some other supplements like sildenafil, ecosprin, G-CSF injection is assessed and vaginal ultrasound is repeated in 3-4 days. If the endometrial lining is not improving, the cause of thin endometrium is looked for.

Some of the causes of thin endometrium can be:

1. Deficiency of the estrogen hormone
2. Poor blood flow to the uterus
3. Damage to the endometrium from previous surgery causing adhesions (uterine synechiae)
4. Infections
5. Lack of physical activity (sedentary lifestyle) etc.

Once the endometrial lining is ready, progesterone hormone is given for 4, 5 or 6 days depending upon the stage of the embryo, to match the “Window of Implantation” for timely attachment of the embryo to the uterus. At last, Embryo transfer is done under USG guidance on the scheduled date.