What are uterine fibroids? Uterine fibroids are a benign condition with a prevalence of up to 20% in women of childbearing age. Fibroids can affect the shape and size of the uterus. The location, size and number of fibroids determine whether a patient has symptoms and whether treatment is needed. Fibroids can be roughly classified into three categories based on their location in the uterus: subplasmic fibroids (the most common), interstitial fibroids, and submucosal fibroids. Uterine fibroids can affect pregnancy in several ways: (1) deformation of the cervix that affects sperm entry into the uterus, (2) changes in uterine morphology and endometrial blood flow that affect embryo implantation and development, and (3) compression of the fallopian tubes by fibroids that affects sperm-egg cell union. Fibroids also have an impact on the success of IVF. Submucosal fibroids reduce IVF success, but subplasmic fibroids have no significant effect. It is not known whether interstitial fibroids have an effect on IVF. Most fibroids do not increase in size during pregnancy and do not affect fertility, however, larger fibroids (>3 cm), fibroids in the placental area, or compression of the uterine cavity by fibroids increase the risk of miscarriage, preterm delivery, abnormal fetal position, and placental abruption, as well as the probability of cesarean section. The need for treatment of fibroids during pregnancy needs to be evaluated by a medical professional. In conclusion, fibroids can affect pregnancy in many ways, such as sperm-egg union, embryo implantation, and fetal growth and development. However, the need for treatment and the treatment measures vary from person to person.