THIN UTERINE LINING
Endometrial lining is routinely measured using the vaginal ultrasound in IVF cycles and is expected to be of adequate thickness for embryo implantation. An endometrial thickness of 8 mm or greater is generally considered adequate thickness and less than 7 mm has been associated with lower pregnancy rates, with almost no pregnancies observed with a lining less than 5 mm.
Poor endometrial lining most commonly occurs in women with a history of unexplained recurrent IVF failures or early recurrent miscarriages and is usually attributable to the following factors:
- Endometritis: Chronic infection of the endometrial cells.
- Fibroids of the uterine wall (non-cancerous muscle tumors of the uterus).
- In-Utero exposure to the synthetic hormone called diethylstilbestrol (DES).
- Women using clomiphene citrate (Clomid, Serophene).
- Scar tissue of the endometrium (Intra-uterine adhesions or formerly known as Asherman’s syndrome).
- Distal tubal blockage (hydrosalpinx) and leakage of toxic fluid back into the uterus.
When thin endometrial lining is observed during an IVF cycle, additional estrogen in the form of vaginal suppositories may improve the overall endometrial thickness and outcome. Some investigators have used baby aspirin to improve the outcome, but results have been quite variable and most likely there is no benefit. Acupuncture and other relaxation techniques may be helpful in some cases, but large scale studies are needed to demonstrate a significant improvement with these treatment modalities. In some cases, the endometrial lining never reaches the acceptable thickness.
Sildenafil (Viagra) is a commonly used drug for erection problems in the male and has been shown to increase the penile blood flow. Investigators have used Viagra to increase the blood flow to the uterus with the hope of delivering more estrogen hormone to the uterine lining. Viagra vaginal suppositories can be used to achieve this goal in IVF cycles, in which the endometrial lining is thin despite additional vaginal estrogen treatment. In most cases of thin lining, the underlining cause can be identified and treated without the need for additional intervention.
Treatment options for specific causes:
In cases of endometritis (infection of the uterine lining), an endometrial biopsy with documentation of chronic inflammation or with bacterial cultures confirms the diagnosis, which necessitates antibiotic treatment. Multidrug treatment for at least 7-10 days is recommended to eradicate chronic inflammation of the uterine lining. A repeat endometrial biopsy is not necessary to document resolution of inflammation and patients can resume fertility treatment within one menstrual cycle.
DES exposure is relatively uncommon in reproductive age women because its use in pregnancy was banned in 1971 in the United States. Although uterine malformations due to DES or most other causes can not be corrected surgically, surrogacy in such cases results in excellent reproductive outcome. If fibroids are present, they can be surgically removed and the uterus can be reconstructed to establish a healthy pregnancy.
Clomid treatment can result in thin endometrial lining because the drug acts as an anti-estrogen at the level of the uterus. In such cases, either additional estrogen is administered along with Clomid or a different type of fertility medication is used. Alternatives are Femara, Tamoxifen or injectible FSH medications. Femara and Tamoxifen are oral medications, but they are not commonly used to induce ovulation or for the purpose of superovulation currently. Although their safety has been established by medical studies, a drug company warning on the use of Femara and risks on the developing fetus has limited its use in women trying to conceive. Among the three options, injectible FSH preparations result in the highest pregnancy rates and successful ovulation can be accomplished 100% of the time.
Intra-uterine adhesions or scar tissue can result from prior uterine infections, pelvic inflammatory disease, multiple uterine procedures, prior termination of pregnancy or postpartum curettage of the uterine cavity. Hysteroscopic diagnosis and treatment of adhesions results in high pregnancy rates in most cases. Mild adhesions are relatively easy to treat, but severe adhesions generally need multiple hysteroscopic procedures to restore a normal uterine cavity. If adhesions are so severe that correction is not possible, surrogacy becomes a viable alternative treatment option.
Distal blockage of fallopian tubes (hydrosalpinx) results in accumulation of toxic fluid inside the tube that can drain back into the uterine cavity. Such drainage of toxic fluid can result in the diminishment of embryo binding sites called integrins in the uterine lining and result in no implantation, thin endometrial lining or miscarriages. It is almost standard practice currently to remove such diseased tissue [removal of blocked tube(s) – salpingectomy] by laparoscopy. Once the drainage of toxic fluid is eliminated, it has been shown that integrins (embryo binding sites) are replenished and pregnancy rates significantly increased.
Pregnancy rates with surrogacy treatment are much higher than patients who are trying to become pregnant and suffer from uterine problems including a thin endometrial lining. Even though surrogacy is the last option and not desirable initially, in some cases it may be the only option. A detailed discussion and evaluation with an infertility specialist is highly recommended in cases of uterine problems, especially thin endometrial lining.
