Question: I have PCOS and have been trying to conceive for six months. I’ve been on Clomid for six months. My doctor is concerned about my uterine lining being so thin when my follicles are at a very good size. She has put me on Clomid and injectables to see if my uterine lining will thicken up. What is a good thickness for uterine lining in order to have implantation and have it stick?
Answer: A large study out of Boston found that approximately 95 percent of pregnancies occurring with Clomid happen in the first four months of treatment. It may be reasonable to ask your doctor about moving to another treatment.
Clomid is considered an anti-estrogen. As such, it is thought that one reason for pregnancy rates that are lower than injectable fertility medications is the adverse effect this may have on the uterine lining. There has been concern that this may cause the uterine lining to become thinner. Although the data is weak, some small studies comparing Clomid to other types of ovulation-inducing medications have sometimes found thinner linings with Clomid.
The lower limit for a uterine lining thickness that will produce a pregnancy is not known. Case reports of women with very thin lining having viable pregnancies are published. In the absence of any solid data, many physicians seem to use a thickness of 7 mm to demonstrate adequacy of the uterine lining.