Angelina Jolie adopted a Vietnamese boy this week in what may be the first of what many officials expect to be a surge of single-parent adoptions in that country.

While national governments such as China are strengthening requirements for foreign adoptions and accepting only married couples, prospective parents like Ms. Jolie are forced to turn to smaller countries with more lenient regulations.

In May, China’s national adoption agency, the China Center of Adoption Affairs, will implement more stringent requirements for foreign applicants. The new policy will bar people who are single, obese, over 55, or who fail to meet specific standards for financial, mental, and physical well-being.

The assistant director of international adoption programs at Spence-Chapin, Jennifer Goodbody, said New Yorkers would be hit hardest by the age restriction.

“The age thing is definitely a factor, especially in New York, where we see a lot of people who are older when they get married or may have been 46-47 when they adopted in the past and wouldn’t qualify anymore if they wanted a second child.”

The Manhattan coordinator for Families With Children From China, Jennifer Maslowski, said new financial requirements would also hurt adoptive parents in the city. After May 1, applicants must have a net worth of at least $80,000 and an income of at least $10,000 a person in their households.

“Because they rent, a lot of people in New York don’t have $80,000 in assets. If you’re renting and you don’t own a home, you might not put your money into things like that,” she said. “Before we bought our first place, we had plenty of money to afford a child, but didn’t have $80,000 in assets.”

Some hopeful parents will be surprised to find themselves caught by one of China’s more specific conditions. While therapy and mental health medications have become common in the city, for example, they can also be grounds for rejection. An outreach director at Children’s Hope International, Cory Barron, said this was “a Catch-22” as infertility and depression are usually linked.

“That’s a very depressing time for people, so their physicians put them on short-term anti-depressants,” he said. “They’re sad, they’re blue because they can’t have a baby naturally, but that disqualifies them from China.”

Same-sex couples were already prohibited from adopting in China: In order to be approved, a single person needed an affidavit signed by a pastor that stated his or her heterosexuality, Mr. Barron said.

Adoption agencies said people who no longer fit the criteria to adopt in China would most likely consider to countries like Vietnam and Ethiopia. Until May, however, many of these applicants are scrambling to beat the approaching deadline. “There are a lot of agencies and facilitators who are dropping everything with everybody else and only helping those who need to get things out by May 1st,” Ms. Maslowski, who adopted her daughter from China with her husband three years ago, said.

After she heard the initial announcement in December, Pamela Huson rapidly assembled her application in two months — an entire month faster than it took her to apply for adopting her first daughter from China two and a half years ago. A real estate broker on the Upper East Side, Ms. Huson is also a single mother who said she was “getting close to the age limit in China.”

She said her agency wanted all materials by today to ensure they were processed before the deadline. Although there was a delay with obtaining an orphan immigrant visa, she said it arrived “at the 11th hour” this week.

Statistics from the U.S. Department of state said that 6,493 of these visas were granted to orphans from China last year, making it the leader in international adoptions. About one-fifth of those children live in the New York area, according to Families With Children From China figures.

A publicist for the Jolie-Pitt family did not return messages seeking comment on the new policies.