Fibroids result from the growth of genetically altered uterine cells. The cells divide over and over again until a rubbery mass forms. The mass can be small; undetectable during a normal pelvic exam. Or, in some cases, multiple fibroids can develop or single fibroids can grow large enough to cause severe pain, bleeding and other symptoms. Fibroids grow fastest when estrogen and progesterone levels are high and that is exactly what happens during pregnancy.

The First and Second Trimesters
During the first and second trimesters, ultrasound may be used to measure fibroids to determine if the masses are growing. This is especially important in women with large fibroids as the mass could alter the shape of the uterus or interfere with fetal placement in the uterus at the start of labor. In rare cases, fibroids have blocked the birth canal.

Third Trimester
The doctor may watch fibroids more closely during the third trimester. If the fibroid presses on the uterus, the pregnant woman may be at increased risk of premature labor. Remember to watch for signs and symptoms of premature labor. The doctor will have information on false labor versus real labor.


In most cases delivery of an infant is not interrupted by fibroids, but in rare cases, fibroid growth interferes with fetal positioning and passage through the birth canal. If there is a fibroid that may affect birth, a C-section will likely be suggested to reduce the risk of complications. Immediately after birth, some women experience heavy bleeding. In most cases, doctors and nurses have no idea how much blood a woman is passing. Report heavy bleeding to the nurse immediately as it could be a complication associated with fibroids.


After delivery hormone levels will return to normal. Fibroid growth should slow or stop. In many cases, fibroids shrink after pregnancy as blood volume and hormone levels return to normal. Keep track of menstrual cycle length and flow. If heavy, prolonged bleeding continues to reappear, report the symptoms to your gynecologist.

Many pregnant women breeze through pregnancy without complications. The biggest threats to fibroid growth are increased blood volume and increased hormone levels. The combination allows for ideal conditions for fibroid growth. Small fibroids may not grow large enough to cause additional symptoms during pregnancy, but growth on some level is likely. Report any symptoms, including back pain, bleeding or cramping to the obstetrician immediately.


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