Most commonly patients undergoing in-vitro fertilization undergo a month of preparation of the ovaries termed down- regulation. This approach allows the ovary to be stimulated with medications to mature multiple eggs. Typically stimulations result in 5-15 eggs maturing so they may be removed. At the appropriate time, the patient is given a light anesthetic so that the eggs may be removed through a procedure which allows the physician to see the ovaries with vaginal ultrasound and "aspirate" the eggs by passing a needle directly into the ovary, applying suction to remove the eggs. Once the eggs are removed they are incubated with the partner's sperm and maintained in an incubator for 3-5 days. At the end of this incubation, the designated number of embryos is returned to the patient's uterus through the cervix. This part of the process is painless and requires no anesthesia. After the embryos are returned to the uterus, a pregnancy test is done about 10-12 days later to determine if implantation has occurred. Any embryos not returned to the woman's uterus may be frozen for possible future transfer.