Women's Health Community

Dear An: I am assuming that you are NOT using some type of hormonal birth control. If you are, then the most likely explanation is some type of breakthrough bleeding due to an unstable lining of the uterus.

The first thing to rule out is an undetected pregnancy. Even an early miscarriage can trigger a positive result on a sensitive urine pregnancy test. If the test is negative then erratic bleeding patterns can arise from either missed ovulations, or a new infection inside the uterus.

As you may know, in a normal cycle, estrogen is produced all month. Estrogen is responsible for building up the lining of your uterus so you have something to shed each month. In a normal cycle, progesterone production increases following ovulation. Progesterone "stabilizes" the uterine lining in preparation for a possible implantation of a new pregnancy. If you are not pregnant that month the levels of estrogen and progesterone fall, triggering the release of the uterine lining—your period. So, if you do not ovulate, the estrogen build up of the lining continues, but without the usual ovulation associated progesterone. Thus, the hormone levels don't decline, and the lining stays up inside the uterus—usually as a late/missed. Alternatively the lining can begin to shed under its own weight producing prolonged bleeding.

In terms of the "tissue" appearance to the clot, commonly when we send such specimens to the lab, the report returns as: white blood cells, red blood cells, fibrin, and other components of uterine lining tissue. It can look different as it is more solid than the liver-like consistence of blood clots. Many women worry that this is linked to a missed miscarriage, but that is not the usual explanation. If this is a concern to you than a sensitive pregnancy test can be done.

VERY rarely a woman will pass a "uterine cast". This is when the lining is passed as a triangular shaped bit of tissue similar to the shape of the inside of the uterus. The predisposing condition for passing a uterine cast is abrupt cessation of high dose progesterone therapy. I have also seen a cast associated with an ectopic/tubal pregnancy.

Bottom line, you should first rule out pregnancy (if you are sexually active). If the erratic spotting persists/worsens, or you develop pelvic pain (eg ovarian cyst or infection) see your GYN. Hopefully your own natural cycle will reset itself since this was a one time incident.

Yours,
Jane