Reproductive disorders encompass abnormalities of the internal gonads, the reproductive tracts, and external genitalia. Hormone imbalances may cause improper development of sexual organs, or poor production of gametes (sperm or ovum). The uterus is also important for implantation of the fertilized egg and development of the fetus. Problems associated with this environment can affect pregnancy and lead to miscarriage. Disorders can also arise due to malnutrition, infection, trauma, tumors, and anatomic causes.