Lawyers for a deported Mexican woman who is eight months pregnant are seeking her return to the United States to protect the unborn baby's health. They also say under federal law the fetus is a viable human being and thus may be eligible for citizenship rights.

That argument sounds like a longshot to some on both sides of the immigration debate. But in May, a U.S. District Court judge in Kansas City, Mo., approved a stay of deportation for a pregnant Mexican woman after raising, among other concerns, the question of whether her fetus could be considered a U.S. citizen. The judge is reviewing the issue.

That Missouri decision cannot set legal precedent, but immigration attorneys say it may offer them a new angle in deportation cases.

Last week immigration officials in Los Angeles denied a request to grant 30-year-old Maria Christina Rubio (search), mother of two young U.S.-born daughters, a temporary humanitarian visa to return to the United States because of complications in her pregnancy.

The request was filed by her husband's attorney, Luis Carrillo. Carrillo said he is considering whether to file a lawsuit against Immigration and Customs Enforcement for unlawful deportation.

Rubio's attorney Alexander Lopez said he had filed a separate visa request to immigration officials in Washington but had not yet received a response.

Carrillo said Rubio, who was hospitalized with complications in her fifth month and has suffered severe stomach pains throughout her pregnancy, needs to be back in the United States because the baby's health is at risk.

He also cited the Unborn Victims of Violence Act (search) of 2004, in which unborn children are granted equal protection under criminal law. Carrillo said that since the fetus is 8 months and would be viable outside the womb, it should be treated as a child born in the United States.

"The child was conceived in the United States and would have been born in the United States except that the mother was deported. Through no part of his own, the unborn baby is in Mexico," Carrillo said.

Virginia Kice, a spokeswoman for Immigration and Customs Enforcement (search), said the U.S. Constitution's definition of citizen is very clear.

"All persons born or naturalized in the United States" are considered citizens under the 14th Amendment.

"It doesn't say all persons who were conceived in the United States," Kice said.

In the Missouri case, the court questioned whether the unborn child would be a U.S. citizen because its father was.

Lawyers for the U.S. Attorney's office in Missouri argued that while fetuses are protected under criminal law, the law does not restrict the government's immigration powers. Known as "Laci and Conner's Law," the legislation was enacted after the bodies of Laci Peterson and her unborn son washed up along the San Francisco Bay in 2003. Peterson's husband, Scott, is charged with their murder.

Rubio was deported July 16 after she went to what her husband says was to be a status conference on her residency request. Immigration officials say the pregnant Rubio was immediately deported after it was discovered her residency request had been denied two years before and that she had previously entered the country illegally.

Lopez, who did not attend that hearing, said he never received notice of the denial and that Rubio had continued to receive work permits.

Kice said Lopez was reached by telephone at the time and did not raise any concerns about Rubio's health. She also said Rubio received an exam from public health services to ensure she was fit to travel.

Alan Diamante, an advising attorney in the case, said he believes it is important to bring the fetus citizenship argument to court, although he acknowledged it may be difficult argument to win.

"You can say this argument is a stretch, but these are the types of arguments that attorneys have to make to get into court," he said. "Laws are always changing and becoming harsher, and immigrant lawyers have to be creative to be heard."