Thin Uterine Lining: Causes and What Can Help

Why does uterine lining thickness matter for pregnancy?

The uterine lining is the tissue an embryo attaches to, and it thickens through each menstrual cycle in response to estrogen. A receptive lining generally looks thick and well-layered on ultrasound near the time of implantation.

Many clinics look for a lining of at least 7 to 8 millimeters before an embryo transfer, though this threshold is a rule of thumb rather than a hard cutoff, and pregnancies happen below it. What matters is a combination of thickness, pattern, and blood flow. According to the American Society for Reproductive Medicine, assessing the uterine cavity is a standard step when evaluating female infertility 1Ref 1Practice Committee of the American Society for Reproductive Medicine (2021).Fertility evaluation of infertile women: a committee opinion.ASRM committee opinion establishing that assessment of the uterine cavity is a standard step in the female fertility evaluation, including when to evaluate after 12 months (or 6 months if age 35+).. Blood flow to the lining, seen on Doppler ultrasound, adds another clue to how receptive it may be.

What causes a thin uterine lining?

Several factors can keep the endometrium from thickening normally, and often more than one is involved. Low estrogen is a common thread, whether from the natural menopausal transition, certain ovulation medications, or hormonal suppression.

Structural causes matter too. Scar tissue from a prior procedure can thin or damage the lining, a problem seen in uterine scarring known as Asherman's syndrome. Chronic inflammation, reduced blood flow, and past infections can also play a role. Because infertility affects about 1 in 6 people of reproductive age according to the World Health Organization, a thin lining is only one of many possible contributors a workup will sort through 2Ref 2World Health Organization (2025).Infertility (fact sheet).WHO fact sheet states about 1 in 6 people of reproductive age experience infertility, framing a thin lining as one of many contributors.. Age-related changes, thyroid problems, and prior pelvic infections can each play a part, which is why the workup looks beyond the lining itself.

Can you get pregnant with a thin lining?

Pregnancy is certainly possible with a thinner-than-average lining, and the number on an ultrasound is not destiny. Some people conceive with linings that measure below the usual target, while others with thick linings do not.

Age remains one of the strongest factors. According to a committee opinion from the American College of Obstetricians and Gynecologists and the American Society for Reproductive Medicine, fertility declines gradually through the early 30s and more sharply after age 37 3Ref 3American College of Obstetricians and Gynecologists / American Society for Reproductive Medicine (2014).Female age-related fertility decline. Committee Opinion No. 589.Joint ACOG/ASRM committee opinion: fertility declines gradually in the early 30s and more sharply after age 37, the strongest age-related factor.. Lining thickness tends to get more attention in assisted reproduction, where clinicians measure it before a transfer. Reviewing your fertility testing results together puts the lining in context alongside hormones and egg supply.

What treatments can help thicken the lining?

Treatment starts by finding and addressing the cause, which is more effective than chasing a target number alone. When low estrogen is the issue, clinicians may adjust hormonal support around a transfer. When scar tissue is found, a minor surgical procedure can restore the cavity.

Other approaches, such as improving blood flow or changing an ovulation medication that thins the lining, are tailored to the person. Evidence for many add-on remedies is limited, and guideline groups caution against unproven treatments. For those using assisted reproduction, timing a frozen embryo transfer to a well-prepared lining is a common strategy. The goal is a receptive lining, not a specific millimeter.

When a thin lining needs a fertility specialist

A reproductive endocrinologist can investigate why a lining stays thin and match treatment to the cause. If you have had trouble conceiving for 12 months, or 6 months if you are over 35, light or absent periods after a uterine procedure, or repeated failed transfers, an evaluation of the cavity is reasonable 1Ref 1Practice Committee of the American Society for Reproductive Medicine (2021).Fertility evaluation of infertile women: a committee opinion.ASRM committee opinion establishing that assessment of the uterine cavity is a standard step in the female fertility evaluation, including when to evaluate after 12 months (or 6 months if age 35+).. Lining concerns look different across life stages: they are unusual in the teens and twenties and more common as estrogen shifts in the perimenopausal years. Care is individualized, and small changes sometimes make a meaningful difference. Gale can help you prepare for that conversation.