Endometrial Thickness: What Is The Normal Range?

Endometrial Thickness What Is The Normal Range

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The endometrial lining of the uterus plays a key role in fertility. Any abnormality in the thickness of the uterine lining could lessen the chances of conception, which can be frustrating if you are planning to have a baby. However, with the many fertility treatments available today, there is hope for the couples dealing with it.

In this post, MomJunction tells you about the issues associated with the endometrium lining, its symptoms, and the ways to deal with it to improve the chances of conception.

What Is The Endometrium?

The endometrium is the inner lining of the uterus where the implantation of the embryo takes place (1). It comprises a single-layered prismatic epithelium and cell-rich connective tissue with blood vessels that surround the uterine glands. The single-layered prismatic epithelium consists of three types of cells: secretory cells, cells with cilia, and basal cells.

The endometrium undergoes various morphological and functional changes during menarche. As the level of sex hormones changes in the body during ovulation, the thickness of the endometrial lining also changes to enable the implantation of the fertilized egg. If fertilization doesn’t happen, then the endometrium lining (functional layer) sheds, leading to menstrual flow.

Note: The morphology and thickness of the endometrium remain constant before puberty and in menopause.

What Does The Endometrial Stripe Look Like?

What Does The Endometrial Stripe Look Like

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The endometrium looks like a stripe on an MRI or ultrasound scan. The stripe refers to the appearance and thickness of the endometrium lining that changes during the menstrual cycle.

Here is how the endometrium changes during the menstrual cycle (2):

  • Menstrual and early proliferative phase: In this phase, it appears as a thin and bright echogenic stripe that consists of a basal layer with minimal fluid.
  • Late proliferative phase: A trilaminar appearance is seen in this phase. It comprises the basal layer, middle functional layer, and the inner echogenic stripe at the center.
  • Secretory phase: Endometrium is the thickest during this phase. The stripe has fluid surrounding it and thus looks uniformly echogenic in an ultrasound.

The following section explains the thickness of the endometrium during various stages of the menstrual cycle.

[ Read: Yoga Asanas That Boost Fertility ]

What Should The Thickness Of The Stripe Be?

Here is how the endometrium stripe’s thickness varies at different stages of the menstrual cycle in premenopausal women.

Stages Thickness
During menstruation2 – 4mm
Early proliferative phase (day: 6-14)5 – 7mm
Late proliferative/Preovulatory phaseUp to 11mm
Secretory phase (ovulation)Up to 16mm

The endometrium thickness must be greater than 8mm for normal pregnancy (3). The pregnancy rate is negatively affected when the stripe’s thickness is less than 7mm (4).

What Causes Abnormally Thickened Endometrium?

Both pregnant and non-pregnant women can have an abnormally thickened endometrium due to various reasons (5).

In pregnant women, thickened endometrium could be due to:

  • Ectopic pregnancy, which can make the endometrium look thick
  • Pseudogestational sac
  • Retained products of conception
  • Heterogeneously thickened endometrium, which could be due to fluid collection
  • Heterogeneously thickened endometrium due to an intrauterine blood clot
  • Molar pregnancy, wherein the multiple small cystic spaces make the endometrium look thickened
  • An inflammation of the uterus, also called as endometritis

In non-pregnant women, it could be because of:

  • Endometrial carcinoma that gives it a thickened appearance
  • Endometrial hyperplasia or over-thickening of the endometrium
  • Endometrial polyp, or benign protrusions on the endometrial surface
  • Tamoxifen-related changes causing variable appearances of the endometrial surface
  • Endometritis

What Are The Symptoms Of An Abnormally Thick Endometrium?

The symptoms of an abnormally thick endometrium lining, also known as endometrial hyperplasia, include (7):

  • Heavier bleeding during periods
  • Longer periods than usual
  • Menstrual cycle shorter than 21 days

For further diagnosis, consult your doctor.

How Is Abnormally Thick Endometrium Diagnosed?

Transvaginal ultrasound helps in identifying abnormal endometrium thickness (6).

How Is It Treated?

Your doctor will discuss the treatment options depending on the cause for thickening. Apart from thickening, endometrium lining could also become thinner than usual, yet another problem faced by many women. Find out more about it next.

What Causes Thinning Of The Endometrium?

Thin endometrium results from the impairment of the normal growth of the endometrial tissues. The most common reason is menopause. The other reasons include (6):

  • Permanent damage to the basal endometrium
  • Resistance of estrogen by endometrium surface receptors
  • Decreased blood flow to the endometrium
  • Testosterone overexposure

Can Endometrial Thickness Indicate Early Pregnancy?

Yes. Endometrial thickness can indicate early pregnancy, be it normal or abnormal (ectopic). Most normal intrauterine pregnancies occur when the endometrium has a thickness of 13-25mm (9).

[Read: Do Ovary Cysts Affect Pregnancy?]

Have you any experiences to share? Please share them in the comments section below.


1. Role and functional anatomy of the endometrium; Universities of Freiburg, Lausanne and Bern.
2. Dr Henry Knipe, Dr Yuranga Weerakkody, et al.; Endometrial thickness; Radiopaedia.org (2005–2019)
3. Moschos E, Twickler DM; Endometrial thickness predicts intrauterine pregnancy in patients with pregnancy of unknown location; NCBI (2008)
4. Fatemeh Sarvi, Marjan Arabahmadi et al.; Effect of Increased Endometrial Thickness and Implantation Rate by Granulocyte Colony-Stimulating Factor on Unresponsive Thin Endometrium in Fresh In Vitro Fertilization Cycles: A Randomized Clinical Trial; Hindawi (2017)
5. Dr. Daniel J Bell and Radswiki et al.; Abnormally thickened endometrium (differential); Radiopaedia.org (2005–2019)
6. Gangadhar Sahoo, Vishy Agrawal et al.; How To Improve Thin Endometrium In Cases Of Female Infertility; Jaypee Journals (2018)
7. Endometrial Hyperplasia; American College of Obstetricians and Gynecologists (2019)
8. Aimee E. Raupp; Yes, You Can Get Pregnant: Natural Ways to Improve Your Fertility Now and into Your 40’s; pg 27,166
9. E. Moschos, D. M. Twickler; Endometrial thickness predicts intrauterine pregnancy in patients with pregnancy of unknown location; International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) (2008)
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