After having difficulty getting pregnant for three years and taking fertility drugs to have my first child, I have been told that I have a septum. I do not quite understand it all. Can you please explain this to me?

--Nina

A septum is a malformation of the uterus that is present from birth. It frequently causes no problems with pregnancy.

To understand about a septum, you need to know a bit about how the uterus is formed. At about two months of pregnancy, the uterus in a female fetus begins to form. It develops from two tubelike structures called the Mullerian ducts. As the baby grows, these tubes enlarge and their middle portions fuse together to form the uterus. The upper portions of these ducts go on to form the fallopian tubes. The fused tubes continue to grow; as the uterus enlarges, the area where the tubes touch each other dissolves, leaving one hollow muscular tube -- the uterine cavity.

It is a miracle how this chain of events happens. Yet things can go wrong. The ducts may not merge; the result is a double uterus. The ducts may merge incompletely, creating a heart-shaped (bicornuate) uterus. One of the ducts may fail to develop, forming a single-horned (unicornuate) uterus with only one fallopian tube. Or the ducts fuse, but the area where they joined does not dissolve, leaving a dividing wall inside the uterine cavity -- a uterine septum.

Septums vary in their size and severity. The septum usually starts at the top of the uterus (the fundus) and can reach down to the uterine opening (the cervix). The larger the septum, the more likely it will interfere with pregnancy. The septum does not have a normal blood supply. It is believed that if a fertilized egg implants on the outer wall of the uterus, it will do just fine. But if it implants on the septum, the placenta may not get enough blood, and this may result in miscarriage or premature labor and early delivery.

Septum can easily be treated by an outpatient surgical procedure called hysteroscopic resection, in which a doctor cuts out the septum. The procedure is usually performed under general anesthesia, but an epidural anesthetic can be used. The doctor may choose to insert a catheter into the uterus to prevent the separate walls of the uterus from joining again with scar tissue. You may also be placed on hormones to speed healing. Success rates from this surgery is high, and most women require no postoperative pain medication.