An investigation into so-called birth tourism — in which hundreds of pregnant women from China paid for all-inclusive trips to Southern California, where they gave birth to American citizen babies — generated a conviction Tuesday, when the first of 19 defendants pleaded guilty to one count of conspiracy to commit immigration and visa fraud.

Dongyuan Li, a 41-year-old Chinese national who lives in Irvine, entered the plea during a hearing in U.S. District Court in Santa Ana. She faces up to 15 years in prison at sentencing on Dec. 16.

Li and the other defendants were named in a series of federal indictments unsealed in January alleging their participation in an elaborate scheme that catered to wealthy Chinese families and Chinese government officials.

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Li admitted that between 2013 and 2015 she ran You Win USA Vacation Services Corp., a birth tourism operator in Irvine and China. The company took money from pregnant foreign nationals – typically from China – and provided them with travel, food, accommodations and entertainment in the United States until those women gave birth. Those children then received birthright U.S. citizenship.

Though exact numbers still aren’t known, You Win advertised that it had successfully helped more than 500 Chinese birth tourism customers obtain U.S. citizenship for their children, according to the federal indictment.

The indictment also states that Li charged each customer between $40,000 and $80,000, and received $3 million in international wire transfers from China. As part of the operation Li used 20 apartments in Irvine, where her customers lived during the weeks before their due dates. In October and November of 2013, she paid some $61,000 in rent on those apartments.

While it is not illegal for foreigners to give birth in the United States, it is illegal to lie on a visa applications about the intent of a visit.

Prosecutors said some You Win customers were coached by the company on how to make false statements on their visa applications and to U.S. immigration officials, according to the plea agreement. Typically, the women told U.S. officials that they were planning to stay in the United States for only two weeks when, in reality, “they planned to stay for up to three months to give birth,” prosecutors said.

“Li further admitted that her customers bypassed U.S. immigration controls by booking two flights – the first from China to Hawaii and the second from Hawaii to Los Angeles International Airport – because they thought it would be easier to clear U.S. Customs through Hawaii,” prosecutors added.

The charges against Li and the other defendants stem from a series of early morning raids conducted in March of 2015, when some 200 federal agents searched 35 homes and apartments and interviewed pregnant women in Irvine, Rowland Heights and Rancho Cucamonga.

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Officials said at the time — and other interviews later showed — that many of the women questioned had come to Southern California as part of organized tours sold to them by Chinese companies.

In addition to housing and counseling on how to dupe U.S. customs, the women also were provided with vacation-style tours of Southern California. For men, that included visits to Disneyland, shopping excursions and fine dining.

The 2015 investigation prompted federal agencies to arrest and later convict an Irvine-based lawyer who worked with the tourism companies, but officials at the time said others named in the indictment were material witnesses.

As part of her plea agreement, Li has agreed to forfeit more than $850,000, a Murrieta residence worth more than $500,000, and several Mercedes-Benz vehicles.

The remaining defendants are either awaiting trial or are fugitives.