Trilaminar Endometrium and Window of Implantation

When you hear a term like, “Trilaminar Endometrium”, you may wonder what it is and how it factors into your efforts to conceive. As it turns out, how thick (or thin) your endometrium lining is an important factor for the implantation of your embryo, especially when you’re going through the in vitro fertilization (IVF) process. Whether you’re going through fertility treatment or not, after reading this blog, you’ll gain more insight into why endometrium lining is an important clue to getting pregnant and what a, “window of implantation” is!

What is an Endometrium?

The endometrium is the lining of your uterus. Every month, your uterine lining ideally thickens. It does this in anticipation of ovulation and the fertilization of the egg, which will become an embryo. For the embryo to have the best chance to implant, it needs a receptive endometrial lining to attach itself to. This is where a trilaminar endometrium comes in. Trilaminar endometrium lining means there can be three defined lines into your uterus and the thickness is the distance between the two external lines, your gynaecologist knows how to measure it. This distance gets thick by hormones stimulus and it’s making the embryo comfortable so it best settles in for the next nine months to create a healthy baby.

How Do You Know If You Have Trilaminar Endometrium?

If you’re a woman who is 35 years old or younger and you’ve been trying to conceive for over a year or if you’re a woman who is over 35 years old and have been trying to conceive for over 6 months, you should consider scheduling a consultation with a doctor. There may be a fertility concern preventing you from conceiving.

During an initial fertility consultation, you and your doctor will discuss your medical history and your family building goals. Blood work will be run to look at various hormones such as your Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Oestradiol and your Anti-Müllerian Hormone (AMH). In addition, a transvaginal sonogram will be performed to look at your ovaries and evaluate and measure your uterine lining to give the doctor a sense of if you have trilaminar endometrium and if is thin or thick endometrium.

Hormonal imbalances, Asherman’s Syndrome or an inflammation you were unaware of can all impact your endometrium lining. Depending on what your doctor feels is best, there are certain situations where some additional diagnostic tests must be taken and some therapies can help thicken thin endometrium lining.

If you have a thin endometrium it doesn’t mean you won’t get a pregnancy but could mean that your window of implantation is displaced.

Whether I have Thick or Trilaminar Endometrium – What’s a Window of Implantation?

A window of implantation is the period of time in which your endometrium lining is at its optimal state to receive an embryo for implantation. According to Dr. Carlos Simon, identifying the window of implantation can be vital in a successful IVF outcome. Since every patient’s window of implantation can be different, your doctor may recommend a test called Endometrial Receptivity Analysis (ERA) to pinpoint your window of implantation.

What is ERA and How Does it Relate to Endometrium?

ERA is a genetic test performed on a very small sample of a woman’s endometrium lining to determine which day would be the best day to transfer the embryo during an IVF cycle. An endometrial biopsy would be taken by your physician and then sent to a lab to be analysed to find your specific window of implantation. This test bases your receptivity on several factors that includes the evaluation the expression of 248 genes. Your window of implantation is so incredibly unique that your reproductive endocrinologist can schedule your frozen embryo transfer (FET) around when your endometrial lining will be at its most optimal for implantation.

According to studies, having an embryo transfer in the right moment guided by ERA, improved pregnancy rates up to 73% in cases when personalized transfers were made, according to the test results (Fertility and Sterility, September 2013). This research suggests that if you’ve had unsuccessful IVF outcomes and you have quality embryos, it may be worth a conversation with your doctor to see if the ERA test is worth exploring.

Ideally, we’d all have a trilaminar endometrium that is thick enough exactly when we’d want and need it. Unfortunately, though, that isn’t always the case and sometimes, we only find that out when we’re actively trying to conceive. If you have had 2 or more unsuccessful embryo transfers, have had concerns with endometrial lining or you’ve had unsuccessful implantation with high quality embryos (meaning embryos that were genetically tested using  PGT-A,formerly known is PGS),  seek help from your doctor to help provide options and support as you build your family.