Fertility • March 26, 2010

Answers to questions about how thick the uterine lining needs to be for an embryo to attach

Terje Sordal

Fertility specialist dedicated to helping patients expand their family and stay informed through evidence-based insights.

So the question was: “How thick does the uterine lining have to be for an embryo to attach?”

To that I can say the following. Many IVF doctors want the endometrium to be 7 mm or thicker before choosing to transfer fertilized and divided eggs (embryo), but as far as I understand from the literature, there is no proven reduced chance of getting pregnant as long as the endometrium is 4 mm or thicker. The desire for a thicker endometrium is often linked to a desire for it to be more similar to what is found “normal” and in most stimulated cycles, and which is perceived as more favorable for achieving pregnancy.

Many will find that doctors have different opinions about what is “best”, both when it comes to stimulation, supportive treatment and the thickness of the uterine lining before the return of fertilized and split eggs. It may be good to know that the scientific content of the “expert opinions” is considered the lowest when it comes to scientific validity. This applies to my private opinions as well as others’, to the extent that they are not based on scientifically valid facts.

COMMENTS · 4

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Terje Sordal November 05, 2018

Nothing is absolute, but normally we expect the endometrium to be most "fertile" between 7 – 10 mm. Next time ask your doctor to measure your oestradiol, LH and progesterone on the day of last ultrasound scan, just to see if there is correlation between oestradiol and endometrium and to exclude elevated LH levels or premature increased pogesterone.

1 answer SVAR
- Terje Sordal Jun 14, 2018
  
  Hi Ramona
  I think it's best to take the test early in the cycle, preferably on day 1-2 of your period.
  
  SVAR
Emma October 05, 2018

Hey,
I used Letrozole from cycle day 3 to 5 and did ultra sound on cycle day 11. My gyno said my uterus lining was thin and it measured 4.7 mm and one follicle of size 19.7 mm on that day. She suggested me to take ovidrel shot on cycle day 12. I read a lot on google that uterus lining 4.7 mm is too thin and not possible for implantation. Is it true? Is there no chance to get pregnant with this uterus lining? What causes the lining of the uterus to be thin? and what can be done to make it normal?
Regards
Emma

SVAR
Terje Sordal May 20, 2010

Hello IVFers and thanks for your questions!

Based on what you describe, I assume that you will be reinserting frozen thawed embryos in a stimulated cycle. Normally, the lining is stimulated to grow by the woman taking Progynova tablets. The dosage can vary, but 2 mg x 3 is often used. In some cases, the lining will not be thick enough for the doctor to want to reinsert. The reason for this may be that the woman's liver breaks down a larger proportion of the estrogen than normal, so that the stimulation of the lining is too weak. In such cases, you can add an estrogen patch or choose to stimulate with an estrogen patch alone. Estrogen that is administered via the skin or via mucous membranes does not pass through the liver first, so the amount of estrogen that is available to stimulate the uterine lining is higher.

In some women, however, the endometrium does not get thick enough. Some have recommended trying Progynova tablets in the vagina. The idea is that much of the estrogen that is absorbed from the lining of the vagina will first pass through the uterus and provide a strong stimulation of the endometrium. The recommended dose is Progynova 2 mg x 2.

It is desirable that the thickness of the endometrium is 7 - 10 mm before deciding to transfer. Some have claimed that it should not be more than 14 mm, while others have found that thickness over 14 mm is not negative. If the endometrium is particularly thick and has a variable echo, one should consider whether there is polyp formation in the endometrium. In that case, this may be negative and should be addressed before choosing to transfer frozen thawed embryos.

If the uterine lining becomes too thick, whatever that means, the solution must be to administer lower amounts of estrogen to reduce the growth.

SVAR
IVFs May 14, 2010

Hi! I have tried several times to get the uterine lining thick enough to insert frozen eggs, but each time the lining becomes too thick. Do you have any suggestions on what I can do? I have tried both progynova and estrogen patches..

SVAR

Answers to questions about how thick the uterine lining needs to be for an embryo to attach

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