Sometimes, a mother may have internal difficulties of her own that can lead to an interrupted pregnancy. One example is a misshapen uterus, in which a woman's uterus is not large enough to accommodate the needs of a growing baby. Some women experience miscarriages (or even infertility), due to non-cancerous tumors in the uterine cavity, which are called submucous fibroids. Others have adhesions, or scar tissue, inside the womb, which can restrict the implantation of the fetus and stunt its growth, leading to a miscarriage. Cervical incompetence is a problem that occurs less frequently, when a weakened cervix shortens and widens, expelling the fetus prematurely.