In the three-plus decades since China implemented its family-planning policies, many couples have opted to have their children outside the country.

But agencies helping Chinese women to give birth in the United States may see reduced business due to the new second-child policy, insiders said.

A year ago, some agencies moved their businesses from the Hong Kong Special Administrative Region to the United States, because the Hong Kong laws forbade non-permanent residents from delivering babies there.

And this year, the businesses took another hit . "We will definitely lose clients, as they can have second children legally in China now," said a staff member surnamed Li at an agency in Beijing.

But some agencies voiced optimism about future business. "Usually, no clients went to the US just for that single reason; after all, it is much more expensive than giving birth in China," said Bai Gang, a staffer at another agency.

Bai said his clients are dealing with various situations, but American citizenship is attractive to them. "So many situations are still not permitted in China now, such as having a third or fourth child," he added.

The fee for flying to the US to give birth ranges from 70,000 ($11,481) to 130,000 yuan.

Saipan, a trust territory of the United States, and Los Angeles are the most popular destinations among Chinese expectant mothers.

More than 10,000 pregnant women from China gave birth in the US in 2012, and the number was close to 20,000 in 2013, said a report from the All America Mother Service Management Center Inc.