The definition is fairly simple – when a couple wants a baby but is unable to have a child because either or both partners are medically unfit to conceive, another woman is artificially inseminated with the sperm of the father.

She then carries the child full term and delivers it for the couple. In such a case, the surrogate mother is the biological mother of the child. In instances when the father’s sperm cannot be used, a donor sperm can also be used. This is traditional surrogacy.

There is also gestational surrogacy, wherein eggs from the mother are fertilised with the father’s/donor’s sperm and then the embryo is placed into the uterus of the surrogate, who carries the child to term and delivers it. In this case, the biological mother is still the woman whose eggs are used, while the surrogate is called the birth mother.

Altruistic surrogacy is when a surrogate is given no financial gain for carrying a child. Only realistic out of pocket expenses are covered by the intended parents, like medical costs, travel, time off work, etc. Altruistic surrogacy can use either a traditional or gestational surrogate.