Fibroids can cause some difficulties during pregnancy, though it is rare. You should be sure that your doctor or midwife is aware that you have fibroids. Fibroids do tend to grow slightly during pregnancy due to the elevated levels of estrogen in the body. Most commonly, fibroids cause some discomfort due to the extra pressure in the uterus. In rare cases the fibroids can lead to pre-term labor or miscarriage. If you experience any sharp pains or bleeding, you should contact your caregiver immediately.