For some couples, an extensive treatment is needed to achieve pregnancy. This is called Assisted Reproductive Technology (ART). With most forms of ART, the sperm and egg are united in the laboratory and the fertilized egg is returned to the woman's uterus where it can implant and develop. Although ART procedures are often costly, many are being used with success. The Donor egg method involves an embryo formed from the egg of one woman (the donor) being transferred to another woman who is unable to conceive with her own eggs (the recipient). The donor relinquishes all parental rights to any resulting offspring. ART using donor eggs is much more common among older women than among younger women. The likelihood of a fertilized egg implanting is related to the age of the woman who produced the egg. Egg donors are typically in their 20s or early 30s.