Endometrial Thickness

What Endometrial Thickness Measures

The endometrium is the tissue lining the inside of the uterus, and it changes shape and thickness across the menstrual cycle. After menstruation, rising estradiol from growing ovarian follicles drives the proliferative phase, when the endometrium regenerates and thickens.^[1] Endometrial thickness is simply the measured depth of that tissue at a given point in time, not a fixed trait of the uterus. It changes across the cycle and looks different from one scan to the next depending on where someone is in their hormonal timeline.

How It's Measured

The measurement comes from a transvaginal ultrasound. The sonographer views the uterus in the sagittal, or long-axis, plane and measures the lining at its thickest point, from the anterior surface to the posterior surface, in millimeters.^[5] It's a quick part of a pelvic ultrasound, not a separate procedure, and it's typically read alongside the rest of the scan rather than on its own.

Why People Track It

Endometrial thickness shows up on ultrasound reports during IVF stimulation monitoring and again before a frozen embryo transfer, as clinics watch the lining develop over several scans. It's a descriptive part of that monitoring, tracked alongside estradiol and other lab values rather than read in isolation. The clinic looking at the full picture, labs plus imaging plus the rest of the cycle, is the one drawing conclusions from it. A single number on a report doesn't mean much without that context.

How Go Go Gaia Tracks Endometrial Thickness

Endometrial thickness comes from a clinic ultrasound, not a wearable or a daily log, so tracking it means recording what your clinic reports. Log the measurement in millimeters with a single tap in Go Go Gaia, and it's charted on your IVF timeline next to your other clinic-reported values, like estradiol and hCG, and your broader cycle data. You get one place to see how your monitoring is unfolding over time.

What the Research Shows

A systematic review and meta-analysis covering IVF cycles found only a modest association between endometrial thickness and pregnancy outcome. Linings the review classified as thin were uncommon, showing up in about 2.4% of cycles studied, and the review concluded that using endometrial thickness alone to decide on cycle cancellation, freezing all embryos, or stopping IVF treatment "seems not to be justified" by the evidence.^[2]

An analysis of more than 40,000 fresh and frozen embryo transfers found that live birth rates were generally lower as measured thickness decreased across the population, but the authors also noted that reasonable outcomes still occurred at the thinner end of the range they studied.^[3] That's a population-wide pattern across tens of thousands of cycles, not a rule that predicts any one person's transfer.

A separate analysis of embryo transfer cycles described endometrial thickness on transfer day as "a poor predictor of IVF success" with "only little independent prognostic value" once other factors, like age and the number of eggs retrieved, were accounted for.^[4] Taken together, the research points to real associations at the population level and genuine disagreement about how much any single measurement should weigh in an individual cycle.

Related Terms

Frequently Asked Questions

Educational information based on published sources. Not medical advice. For personal concerns, please consult your doctor.

How is endometrial thickness measured?

It's measured with a transvaginal ultrasound. The sonographer views the uterus in the sagittal, or long-axis, plane and measures the lining at its thickest point, from the anterior to the posterior surface, in millimeters.

Why do fertility clinics track endometrial thickness during IVF?

It's a routine part of cycle monitoring in IVF and frozen embryo transfer, tracked alongside estradiol and other lab values as the lining develops. The clinic reads it together with the rest of the monitoring picture, not as a standalone number.

Does a thicker endometrial lining mean a better chance of pregnancy?

Research on this is debated. Large studies find population-level associations between a thinner lining and lower pregnancy rates, but systematic reviews describe endometrial thickness as a poor independent predictor for any one person's cycle, and caution against using it alone to decide whether to proceed with a transfer.