The Michael Bianco  raids mentioned by Bryanna on March 7th have produced a large number of news stories about "families being separated." Apparently the illegals being deported are abandoning their anchor babies in the United States, and blaming US immigration law for the abandonment. The Associated Press writes that
Toddlers stranded at day care centers or handed over to ill-equipped relatives. Siblings suddenly left in charge of younger brothers and sisters.
When illegal-immigrant parents are swept up in raids on homes and workplaces, the children are sometimes left behind - a complication that underscores the difficulty in enforcing immigration laws against people who have put down roots and begun raising families in the U.S.
Three million American-born children have at least one parent who is an illegal immigrant; one in 10 American families has mixed immigration status, meaning at least one member is an immigrant here illegally, according to the Pew Center for Hispanic Research and the office of U.S. Rep. Jose Serrano. Children born in the U.S. are automatically American citizens and are not subject to deportation.
Of course, any woman who commits a crime and gets arrested will be separated from her kids, at least temporarily. And the immigration authorities could make provision for the mothers to have their kids with them in detention. (If the Japanese Internment policy of World War II hadn't allowed Japanese parents to take their American kids with them to detention, that would have have been considered inhumane by Eric Muller. )
And in fact, the authorities have released 60 women on humanitarian grounds, to care for their American Citizen children.
But there's a lot of sob-storiness in the air--this is from the Boston Herald:
If the scene that unfolded Tuesday morning had been beamed around the world on live TV, it is very unlikely that anyone would have guessed they were watching the United States of America. Lady Liberty lifting her lamp beside the golden door has given way to federal agents lifting their guns by the factory gates. The lives of the poor and the spirit of America are being destroyed as a result. No matter what our positions on “illegal” immigrants, surely we can all agree that people should never be treated like this.
[Sweatshop raid un-American: City in chaos and families separated  By Thomas Keown, Boston Herald, March 12, 2007]
And there's a story in the LA Times titled Mayor criticizes raid for disrupting families. [By Erika Hayasaki, March 9, 2007]
It's VDARE.com's position that family reunification can take place on either side of the American border. Peter Brimelow , who was born in England, was still a British subject when his son was born in New York . If he had left the United States to return to England, presumably he would have taken his son with him.
There are American expatriates all over the world, whose children are born in France, or Japan, or Korea. They wouldn't think of leaving their kids behind.
But apparently there are immigrants in America who do. The most recent sob story case was that of Ken Sah, who was deported to India and left his 13-year old son who's competing in the National Spelling Bee  behind. Overlawyered.com has a story on him. The reason he has a 13-year old American-born son is that he overstayed his visa in 1991, and has been keeping a bogus asylum claim going for fifteen years. He claimed to fear Muslim persecution if he went home, and as Overlawyered.com  puts it
That might engender sympathy—until one realizes that his home country is India, which has 800 million fellow Hindus for Sah to live amongst. And that Sah's basis for fearing persecution was because, as a member of the radical Hindu nationalist organization Vishwa Hindu Parishad, he "took a very active part in organizing and conducting [anti-mosque] meeting[s]" and that he "actively participated in the riots to [attempt to] demolish the Babri Mosque." (Vishwa eventually succeeded in destroying the mosque in 1992, causing religious riots that killed 900 people.)
The Sahs are now engaging in a public relations campaign for citizenship on the basis of the hardship created by the fifteen years they spent in the country churning the bogus asylum application. None of the press coverage mentions Ken Sah's role in his asylum denial as a radical Hindu. Don't believe the hype.
Ken Sah, spelling bee father 
The language "actively participated in the riots to [attempt to] demolish the Babri Mosque " is from the decision to deport him.[Sah v. Gonzales (10th Cir. 2005] How did the government find out about this? He put it on his asylum application.
But that's not my point. The point is that parents don't have to leave their kids behind when they leave.