When carrying a pregnancy to term is not possible for a woman, she may opt to have a surrogate carrier. This process may use any of a number of combinations of egg and sperm, depending on the situation and fertility of involved parties. Eggs may be acquired from the woman and fertilized in vitro, then implanted in the surrogate. The woman’s partner’s sperm may be artificially inseminated into the surrogate, and fertilize the surrogates egg. Sperm may also be from a donor.