The Endometrial Lining Dilemma: One of Many IVF Decisions Without a Clear Answer
When you’re in the thick of IVF, decisions feel endless and urgent. And sometimes, what seems like a small number—like the millimeters of your endometrial lining—can carry the emotional weight of your entire cycle. This recent study, published in Fertility and Sterility (2025), explores whether we need a new threshold for endometrial thickness. But it also highlights just how fraught these decisions can feel when your options are limited, your emotions are raw, and time feels scarce.
Key Findings
More is better—up to a point. The study found that live birth rates consistently increased with endometrial thickness across all transfer types (fresh, frozen, and PGT-tested), peaking between 12–14.9mm. After that, the benefit plateaued.
The traditional 7mm threshold may be outdated. While 7mm has long been considered the minimum for a “receptive” lining, outcomes were better in patients whose linings measured closer to 9mm or more.
Your transfer type might matter. The benefit of a thicker lining applied across all categories—whether the embryo was fresh, frozen, or genetically tested—indicating that the pattern holds broadly.
Natural vs. programmed cycles could make a difference. The study raised the question of whether endometrial linings in natural cycles are more physiologically optimal, even when thinner, compared to programmed cycles with hormonal support.
No one-size-fits-all. While the data show a trend, there’s still no guarantee. Some patients with “ideal” linings may not conceive, while others with thinner linings might. It’s about pattern, not prediction.
Why This Matters
In my work with clients, I see how often people are asked to make big decisions with incomplete information. Do you cancel a cycle if your lining is 7.2mm? Do you transfer your only embryo after already canceling due to lining thickness? Do you wait again? Do you think about surrogacy? These are not just clinical calls—they’re deeply emotional decisions that can bring up grief, fear, urgency, and the pain of comparison.
This study challenges the idea that 7mm is a "green light." It may be true that thicker linings correlate with better outcomes—but that doesn’t mean thicker is always possible. And when you've already had losses, when your friends are moving ahead, and your embryos are limited, the idea of waiting for a "better" cycle can feel unbearable.
And it’s just one of many decisions patients face in fertility care that don’t have a clear right answer. Timing transfers, choosing protocols, deciding when to pause—so many moments are filled with uncertainty. And when there’s no obvious best path, the pressure to choose "correctly" can be overwhelming.
So what then? You do the best you can with what you have. And you try to quiet the voice that says there’s a perfect answer—because sometimes, there just isn’t. There’s just the next right step, taken with as much care, support, and self-compassion as you can muster. This work is hard. Having a therapist sit with you in those decisions can be a helpful way to sort through the overwhelm and reconnect with what feels right for you.
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