Function

• Your uterine lining grows thicker each month following ovulation and peaks in thickness a few days before your period if you are not pregnant. According to Ferring Fertility the hormones progesterone and estrogen control the thickness of the uterine lining. If the lining is too thin your body will have difficulty maintaining a pregnancy, so an endometrial biopsy is often done as part of a broader infertility treatment plan.
  
  

How it Works

• An endometrial biopsy should be performed one to four days before your period is expected to begin, when the uterine lining is at its thickest. Your doctor will open your vagina with a speculum and use an endometrial catheter to remove a small sample. You may feel pinching or cramping during the procedure, which usually only takes seconds to complete.
  
  

Side Effects

• According to the Ferring Fertility Clinic, cramping is common following the procedure and you may have some spotting, which could last through when your period is expected to begin. Because an early pregnancy could potentially be disrupted by the endometrial catheter, your doctor may give you a blood test, which can discover pregnancy before your first missed period, to be sure that you are not pregnant. There is a slight risk of infection following the procedure, and some doctors will recommend taking an antibiotic afterwards.
  
  

Analysis

• According to the Huntington Reproductive Center the tissue from the biopsy is sent to a pathologist who will examine it according to the specifications of why the procedure was done. For infertility analysis the pathologist will date the tissue according to where it would be during a normal menstrual cycle. The lining is considered in phase if it correlates with the thickness it should be towards the end of your cycle. If your period occurs later in the month than usual, you should tell your doctor, as this could affect the interpretation of the results.
  
  

Warnings

• Although the risk of miscarriage did not increase for women who accidentally had an endometrial biopsy done while pregnant, according to the Huntington Reproductive Center, the procedure is not recommended for any pregnant women. You should not have an endometrial biopsy done if you have pelvic inflammatory disease, any type of vaginal infection, clotting disorders, cervical stenosis or cervical cancer.