"If you can pay, you can play."

This is the pitch circulated in Chinese online "birth tourism" forums to encourage expectant mothers to get on airplanes and have their babies in the United States.

As of Tuesday, however, it might get harder to play, even if you can pay.

US Immigration and Customs Enforcement (ICE) agents on Tuesday morning raided 20 "birthing centers", or "maternity hotels", to collect evidence for suspected visa and tax fraud. The centers are believed to be helping Chinese women travel to the US solely to give birth.

Since Tuesday noon, phone calls to around 10 such "maternity hotels" have been unanswered. A few calls to the firms' Chinese mainland or Hong Kong offices were answered but abruptly hung up.

"Yesterday I saw a pregnant Chinese woman walking in the street, but today I found no one," said Wang, a resident of Rowland Heights, Los Angeles County.

"And the woman I saw seemed very cautious," she said.

"Usually, pregnant women were seen everywhere, in the streets, shopping malls," she said. "They seemed pretty wealthy, I often saw them produce a stack of cash when checking out at cashiers."

From the street, "birthing centers" look no different from ordinary residences, as the operators usually rent apartment suites or houses to accommodate the mothers, said Wang, who has friends in the business.

"One of my friends first started their business by renting the bedrooms of her own house to those mothers, and as more business came, she began renting houses," Wang said.

"A mother is usually charged 200,000 yuan (about $32,000) for a stay of four or five months," said Wang.

The "birthing centers" business was started 10 years ago by business savvy immigrants from Taiwan. The early operators have developed all-inclusive packages and services, from coaching on visa application "techniques" to applying for US passports for the babies. They have offices in major cities like Beijing, Guangdong, Taiwan and Hong Kong.

"Some of the early operators have made big fortunes," said Wang.

According to Chinese media reports, the number of Chinese women who travelled to the US to have babies has increased 100 times over the last 10 years. In 2007, the number was 600 and rose to more than 10,000 in 2008, when the US eased its visa processing for Chinese individuals.

It was expected that 60,000 Chinese women were going to give birth in the US this year.

A birthing center called "Star Baby," which was among those raided on Tuesday, said on its website that it has "recorded more than 6,000 successful cases in last 10 years".

However, the booming business suddenly came to a halt on Tuesday.

News of the federal agents' raid was widely circulated among Chinese communities in the US through social network app Wechat.

"The mothers have been told not to go out," said Wang. "The hotel operators do the shopping for them."

Although it's not necessarily illegal for pregnant foreign nationals to enter the US, the practice of "birthing centers" is exposed to crimes like visa fraud, tax evasion and money laundering as large amounts of cash are transacted, mostly outside of the US.

Neighborhoods that host the birthing centers have opposed the business, charging that the mothers are taking advantage of the federal benefits.

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