When Brad Hoylman and his husband wanted to start a family, they looked to a woman nearly 3,000 miles away to carry their child.

The Manhattanites turned to a surrogate in California, a state with a robust commercial surrogacy industry, because the practice is banned in New York.

The advent of same-sex marriage, advances in reproductive technology, and the fact that more people are waiting longer to start families have fueled a surge in the surrogacy industry.

In 2015, 2,807 babies were born through surrogacy in the U.S., up from 738 in 2004, the American Society for Reproductive Medicine said. Women are often paid at least $30,000 to carry a baby created from the egg and sperm of others.

But in many places, once the baby arrives, outdated state laws fail to answer an important question: Who are the parents?

In many states the law is murky or even silent on surrogacy. The industry is free to operate but the contracts signed between surrogates and intended parents may not be legally binding. The baby may be born in a state that views the woman who gave birth as its mother, even if she has no genetic connection to the child.

The legal uncertainty is particularly concerning to the intended parents, who usually spend about $100,000 and risk ending up without the child they counted on. Male couples have an additional fear: that they might be discriminated against if they are embroiled in a legal fight over custody.

In states that ban commercial surrogacy and those with no laws at all, legislators are pushing bills that would legalize the practice, determine parentage before a child arrives, and ensure that contracts are enforceable and followed by all parties. In many cases, they would require surrogates to be at least 21, to have given birth to their own children, and to undergo medical and psychiatric evaluations before signing a contract.

Surrogacy became legal in Washington, D.C., in April, and lawmakers in Minnesota and Massachusetts debated bills this year but didn’t approve them.

Critics of surrogacy object to what they view as the commodification of women and children. Opponents point to numerous European countries that have banned the practice.

For many, the financial aspect of surrogacy is most troubling. “Women will be exploited by wealthy people,” said Jason Adkins, executive director of the Minnesota Catholic Conference.

Minnesota has no laws on the books governing surrogacy, yet it has a robust industry. Couples often go through a multistep process to obtain custody, said Steve Snyder, a lawyer who owns a surrogacy company. The process is especially fraught for gay male couples who fear they may not get the necessary judicial approval.