5.3.10 Understanding Thin Uterine Lining When Starting Your Surrogacy Journey

1. Understanding the Uterine Lining (Endometrium) in Surrogacy

The uterine lining, or endometrium, plays a critical role in the success of embryo implantation during surrogacy. A properly developed endometrial lining provides the necessary environment for an embryo to attach and grow, making it an essential factor in achieving a healthy pregnancy.

At GSHC Surrogacy & Egg Donation, we prioritize the health and well-being of both the surrogate mother and the intended parents by ensuring that all medical criteria, including endometrial health, are met before proceeding with an embryo transfer.

2. What Causes a Thin Uterine Lining?

In most cases, a lining is considered “thin” if it measures under 7mm on ultrasound, although some clinics may use slightly different cutoffs—like 6mm or 8mm—depending on their protocol.

There are a few common reasons why the lining may not thicken enough:

• Low estrogen levels. Estrogen helps the lining grow. If there isn’t enough, it might not reach the level needed for transfer.
• Poor blood flow. Scarring from past procedures (like a D&C), uterine surgeries, or other medical issues can affect circulation to the uterus.
• Infections or inflammation. Chronic infections, like endometritis, can damage the uterine lining over time.
• Hormonal imbalances. Conditions like PCOS, thyroid issues, or even early menopause can interfere with normal growth.
• Certain medications. Long-term use of drugs like Clomid may thin the lining in some people.

3. Medical Approaches to Improve Endometrial Thickness

For surrogacy candidates with a thin uterine lining, medical interventions may be recommended to improve endometrial thickness before confirming their eligibility for embryo transfer. These interventions may include:

• Estrogen Therapy (Estrace, Patches, or Injections) – Used to stimulate endometrial growth.
• Blood Flow Enhancers – Viagra suppositories, L-Arginine supplements, and acupuncture may help increase uterine blood circulation.
• Hysteroscopy – A procedure used to evaluate and remove potential uterine abnormalities, including scarring.
• Lifestyle Modifications – A nutrient-rich diet, hydration, regular exercise, and avoiding smoking can help improve overall uterine health.

4. What Happens If a Surrogate Mother’s Uterine Lining is Thin?

If your uterine lining appears thin during the initial medical screening, the fertility doctor will first try to understand the cause. In most cases, they’ll recommend a course of estrogen treatment (like Estrace) to help the lining thicken. Sometimes, they’ll monitor you across more than one cycle to see how your body responds.

But if the lining stays thin—even after hormone treatment—the doctor may determine that it’s not ideal to move forward. In that case, the intended parents may be advised to consider working with another surrogate, and you may not pass medical clearance for this journey.

It’s not always an easy outcome, but the goal is to protect your health and give the intended parents the best possible chance of a successful pregnancy. Every clinic is different, and your case will be reviewed carefully before any final decision is made.

5. Hormonal IUDs and Uterine Lining During Medical Screening

If a surrogate mother has a history of using a hormonal IUD like Mirena or Kyleena—or has recently had one removed—her uterine lining may appear thin during medical screening or before embryo transfer. This is a common effect, as hormonal IUDs work by thinning the lining to prevent pregnancy.

After IUD removal, the body may need time to naturally rebuild the endometrial lining. Doctors may recommend waiting a few menstrual cycles to see if the lining improves on its own. In some cases, medication is used to help thicken the lining.

If the lining doesn’t respond well after treatment or time, the clinic may suggest postponing the process or rematching the intended parents. This decision is based on ensuring the best chance for a healthy pregnancy.

Next Steps for Surrogates with a Thin Lining

For prospective surrogate mothers, a thin uterine lining does not necessarily mean disqualification. Each case is evaluated individually, and treatment success rates vary among individuals. The medical team at GSHC Surrogacy & Egg Donation will carefully assess the surrogate's response to therapy before making a final determination.