Did you ever think about what happens inside your uterus each month? The lining of your uterus is called the endometrium. It transforms every cycle to prepare your uterus for a possible pregnancy. But what happens if the lining is too thin, or too thick? Can it affect fertility or signal an underlying condition? In India, infertility affects nearly 13% of couples in their reproductive age. So, yes, a thin or thick uterine lining is one of the reasons why you could be facing difficulties getting pregnant. Keep reading to learn about endometrial thickness, its normal size, the causes & risks of a thin or thick lining, and effective treatment options.
What Is Endometrial Thickness & Why Does It Matter?
The endometrium is the inner mucous membrane lining of the uterus. Its thickness (also called endometrial thickness, or EMT) fluctuates throughout the menstrual cycle under the influences of estrogen and progesterone.
The normal range of uterine lining thickness is important for embryo implantation, proper menstruation, and a healthy pregnancy. Too thin or overly thick lining can result in problems, such as infertility, poor implantation, irregular bleeding, or increased risk of pathology (hyperplasia or cancer).
Normal Range of Endometrial Thickness (in mm)
The normal size of the endometrium in mm depends on age, phase of the menstrual cycle, and post-menopause status. Here are widely accepted reference values:
| Stage / Situation | Typical Endometrial Thickness | Notes / Significance |
| Menstruation/early cycle (Day 1-4) | ~ 1 – 4 mm | In the shedding phase, the lining is thin because of recent menstrual flow. |
| Early proliferative phase (around Day 5-7) | ~ 5 – 7 mm | Estrogen rising, lining rebuilding. |
| Late proliferative phase / just before ovulation | ~ 7 – 11 mm | Optimal prepping for potential fertilization. |
| Secretory phase (after ovulation, before menses) | ~ 10 – 18 mm | Lining is maximally prepared to receive an embryo. |
| Postmenopausal (no hormone therapy) | ≦ 3 – 5 mm (often “3 mm or less”) | A thin lining is expected; more thickness raises suspicion. |
| Postmenopausal with hormone use | Up to ~8 – 11 mm in some cases, but it depends on therapy type and risk factors. |
How Endometrial Thickness Is Measured?
Once your gynaecologist assumes any fertility issues because of endometrial thickness, you might have multiple questions about how to measure its thickness. So, here’s a simple overview for your reference:
- Usually, your doctor will perform a transvaginal ultrasound (TVUS), which gives clearer images of the endometrium (anterior-posterior thickness) on a long-axis view. ● The measurement for the normal thickness is taken as the double thickness of the endometrial echo-complex, which means both the front and back layers of the lining are included.
- Timing matters too. The thickness naturally changes depending on the menstrual cycle. It is different in the proliferative phase compared to the secretory phase
- Sometimes sonohysterography (ultrasound with saline infusion) is used if there’s doubt about the lining’s shape or presence of polyps, etc.
- In postmenopausal or symptomatic women, if ultrasound shows thickness beyond established safe thresholds (often ~4-5 mm), further evaluation (biopsy) may be needed.
What is the Meaning of Thickened Endometrium vs Thin?
Thin Endometrium (often <7 – 8 mm in fertility settings, or <5 mm depending on cycle phase):
- It may reduce the chances of embryo implantation in IVF or frozen embryo transfer cycles.
- Thin endometrium occurs due to several reasons. For example, low estrogen levels, poor uterine blood flow, previous uterine surgery (like curettage), Asherman’s syndrome, use of certain drugs (clomiphene, etc.), or structural issues.
Thickened Endometrium (more than normal for the cycle phase, especially postmenopause, when it should be thin):
- This can result in heavy or irregular bleeding.
- A thickened endometrium also indicates hyperplasia (overgrowth), polyps, or, rarely, cancer. Particularly in postmenopausal women with bleeding, thickness over ~4 mm is considered significant.
- Also, it can be affected by hormonal imbalances, obesity, estrogen therapy, tamoxifen (used in breast cancer), etc.
Relation Between Endometrial Thickness & Pregnancy
For those trying to conceive, especially via ART, an endometrial thickness of ≥7-8 mm is often considered desirable. Below that, implantation rates tend to drop. A systematic meta-analysis (2024) confirmed that EMT ≤7 mm has a significantly lower clinical pregnancy probability compared with thicker linings.
The secretory phase (post-ovulation) is the phase when the endometrium should be thickest, to allow embryo embedding. Suboptimal thickness here can impair implantation and early pregnancy maintenance.
Endometrial Thickness Before Periods
Right before menstruation (end of secretory phase), the lining is at or near its thickest (e.g., ~10-18 mm). If it remains very thin just before the period, this may indicate hormonal imbalance, insufficient estrogen effect, or pathology. Also, some women may see spotting or irregular flow if the lining doesn’t build sufficiently.
Treatment Options for Thin Endometrial Lining
When the endometrium is too thin, especially in fertility/ART settings, there are various strategies. Some are more established, others are emerging. Here’s what research shows:
| Treatment / Intervention | What is Done | Evidence & Effectiveness |
| Hormone therapy (estrogen supplementation) | Oral/transdermal estrogen to raise estrogen levels, sometimes followed by progesterone | Widely used and helps in many cycles. But the magnitude of response can vary, especially if underlying uterine blood flow or structural problems exist. |
| Tamoxifen protocols | Using tamoxifen early in the cycle (for example, in IUI or FET cycles) to stimulate endometrial growth | A 2023 study showed that in patients with prior thin lining (<8 mm), tamoxifen plus estrogen improved endometrial thickness in ~95% of cases, and the pregnancy rate rose (~44.3%) in that group. |
| Growth factors / PRP (Platelet-Rich Plasma) infusion | Intrauterine infusion of PRP to enhance growth factors locally | Experimental but promising; multiple small studies show improvement in thickness and implantation rates. |
| Cell-based / stem cell therapy/bioengineering approaches | Stem cell-derived exosomes, regenerative medicine strategies to repair or regenerate the endometrium | Still mostly in early or pilot trials, but results look promising |
| Addressing structural causes | E.g., surgical correction of intrauterine adhesions, removal of polyps, and optimising the uterine environment | Very important: treatments only work well if underlying issues are identified and remedied. |
What to Do If Your Endometrial Lining Is Thin or Thickened?
Once the problem with your endometrial lining is identified, you would probably want to make it normal. But what strategies should you follow? How to increase endometrial thickness? Let’s find out:
- Track cycle with ultrasound under the guidance of a fertility specialist or gynaecologist.
- Check hormonal profile (estrogen, progesterone) to see if there is an imbalance.
- Assess uterine structure with ultrasound or hysteroscopy if suspect adhesions, polyps, or fibroids.
- Adopt Lifestyle modifications, such as good nutrition, maintaining a healthy weight, reducing stress, and avoiding toxins. Obesity and metabolic disorders can increase the risk of abnormal thickness.
- Use of therapies as above (hormones, tamoxifen, PRP, etc) in appropriate settings.
- In case of thickened lining, especially postmenopause + bleeding, biopsy/histopathology is often recommended to rule out malignancy.
Get the Personalised Advice for Unusual Endometrial Thickness!
Endometrial thickness isn’t just a number on an ultrasound. It reflects your hormonal balance, uterine health, and fertility potential. When the lining is too thin (often <7-8 mm in fertility settings) or unusually thick (especially postmenopause), there are several medical, surgical, or lifestyle-based
ways to address the issue. Exciting new options like PRP and stem-cell therapy are also showing promise for women struggling with recurrent issues.
If you are concerned about your lining, menstrual flow, fertility, or postmenopausal symptoms, it’s wise to talk to a specialist. At Femcare Fertility, our experts use advanced imaging, hormone tests, and recommend the right treatment plan. Your uterus (and your hopes) deserve that care.
FAQs (Frequently Asked Questions)
Question: What is the endometrium thickness and its normal range?
Answer: Normal thickness varies with cycle phases. It’s 2 – 4 mm during menstruation, 5 – 7 mm in the proliferative phase, and 7 – 16 mm in the secretory phase. After menopause, under 5 mm is considered safe.
Question: What if the endometrial thickness is 7 mm?
Answer: A 7 mm thickness is generally acceptable, especially around ovulation, but in fertility care, it’s borderline thin. Doctors may recommend monitoring or supportive therapies to improve implantation chances.
Question: What thickness of endometrium is related to cancer?
Answer: In postmenopausal women, an endometrium thicker than 4 – 5 mm may raise concern. Persistent thickening, especially above 11 mm, is linked to a higher risk of endometrial hyperplasia or cancer and requires evaluation.
Question: Should I worry about a thickened endometrium?
Answer: Not always. A thick lining can be normal during certain menstrual phases or pregnancy. However, if you are postmenopausal or have unusual bleeding, consult your doctor for safe evaluation
Question: What is the ideal endometrium thickness for pregnancy?
Answer: For successful implantation, an endometrial thickness of 7 – 8 mm or more is generally preferred. A triple-line pattern on ultrasound during ovulation also increases the chances of a healthy pregnancy outcome.