The laws on surrogacy vary markedly between different countries - and even within individual countries - in a murky system that can leave children and mothers vulnerable, particularly those in poorer countries.
Some nations, such as Germany, Spain and France, ban surrogacy altogether.
China also bans the practice but reportedly has a flourishing black market, with about 10,000 babies born a year.
Canada (aside from Quebec), Britain and Australia allow it but only if the birth mother carries the child for altruistic reasons and does not receive any payment beyond medical costs.
But places such as India, Russia, Ukraine and some parts of the United States allow commercial surrogacy, where the mother is paid. There are also countries such as Thailand, where there has long been lax regulation and oversight. Thailand has no laws expressively allowing or forbidding the practice.
However, there are proposals to ban commercial surrogacy, and limit such arrangements to heterosexual couples.
Advertisement of surrogacy may also be made illegal, and surrogacy may be undertaken only by parents who had had at least one child, according to a report last week by Thai broadcaster PBS.
The availability of paid surrogacy in some countries but not in others has led to the growth of international surrogacy and a "reproductive tourism industry".
The industry has proven controversial, particularly due to the legal differences from country to country. There have been cases where surrogate parents have paid for a child but refused to take it. There have also been cases where the surrogate mother's country and the biological parents' country take a different position on the nationality of the child.
Some countries have moved to ban their citizens from using surrogate mothers abroad. Others allow it, but impose few or no rules on the parents.
In Australia, states such as New South Wales forbid people to go abroad and pay a surrogate. Anyone who does so faces two years in jail.
But in other states such as Victoria, commercial surrogacy abroad is permitted, though there are no rules or enforceable guidelines.
This article was first published on August 5, 2014.
Get a copy of The Straits Times or go to straitstimes.com for more stories.