Sheng Hailin, 60, gave birth to twins through in vitro fertilization. GUO CHEN/XINHUA 

Worldwide differences

Rules on surrogacy vary from country to country, which can lead to pitfalls and complications for would-be parents.

United Kingdom: It is legal to use a surrogate mother but couples can only pay reasonable expenses. Using a foreign surrogate mother is not explicitly outlawed, but a couple bringing a child born of a surrogate mother into the UK must apply for a parental order to have parental rights.

India: Having a surrogate mother as commercial surrogacy is legal, and the costs are significantly lower than in developed nations. Since 2013, would-be parents traveling to India must have a surrogacy visa, which are only available to heterosexual married couples living in a country that accepts cross-border surrogacy.

Sweden: Surrogacy is not clearly regulated in Swedish law but it is illegal for the country's fertility clinics to make surrogate arrangements. The legal procedure most equivalent to it is making an adoption of the child from the surrogate mother. However, the surrogate mother thereby has the right to keep the child if she changes her mind until the adoption. But the biological father may also claim right to the child.

Canada: The Assisted Human Reproductive Act permits only altruistic surrogacy: Surrogate mothers may be reimbursed for approved expenses but payment of any other consideration or fee is illegal. Quebec law, however, does not recognize surrogacy arrangements, whether commercial or altruistic.

Other countries: It is also legal to pay surrogate mothers in Ukraine, Georgia and Russia. But the practice is banned in many countries, including Germany, Italy and France.