The uterine lining is the site of embryo implantation, so a healthy lining is essential for pregnancy. The uterine lining is shed each month as menstrual flow, which is blood mixed with tissue and cellular debris. The average lining thickness after the menstrual period ends is around 3 millimeters; the lining thickens under the influence of estrogen and normally reaches a thickness of 6 to 13 mm by the time of ovulation, according to the Advanced Fertility Center of Chicago. If the lining is thicker than 15 mm, the embryo may have trouble implanting. Uterine lining measurements can be done via pelvic ultrasound. An overly thick lining is known as endometrial hyperplasia.

Assess the uterine lining by having an ultrasound done. Ultrasounds are non invasive, painless and accurate. If your lining is abnormally thick at this point, medications may be prescribed so that the lining will be shed.

Take prescribed medications to shed the lining. Medroxyprogesterone, a synthetic form of progesterone, is often prescribed for 14 days and then stopped so that a menstrual period will start, since progesterone is the hormone that keeps your period from starting. If you’re not producing enough estrogen during your cycle, your doctor may prescribe estrogen along with the medroxyprogesterone, or birth control pills in a formulation that includes both synthetic estrogen and progesterone.

Recheck your uterine lining via ultrasound once your period starts. If the lining is still thicker than normal, talk to your doctor about the next step. He may recommend doing an endometrial biopsy, where a small piece of the lining is removed and tested to be sure there are no abnormal cells that could be causing the thickening.

Undergo endometrial biopsy, if your doctor suggests. This procedure is often done between days 22 and 24, when you theoretically might be pregnant, but according to Main Line Infertility, the chances of this are low.

Consider birth control pills for several months, if the biopsy shows no problems. Your doctor may suggest birth control pills or estrogen and medroxyprogesterone for several months to thin the lining and keep it from building up again.

A dilatation and curettage, also known as a D&C, can remove the thickened lining, if no other method works, according to Women’s Clinic Ltd. IVF-Fertility Division. The lining is scraped off in a surgical procedure. As soon as your doctor says it's OK, you can try and get pregnant.