Lisa Loomer's energetic, funny, yet heartbreaking tragicomedy about a Latina nanny and her employer, first produced in LA two years ago, is dazzling in this joint Teatro Vista-American Theater Company production, directed by Cecilie Keenan. The employer, Nancy, is a wealthy entertainment lawyer who wants to treat her baby's caregiver, Ana, as a member of the family. But Ana, a married immigrant, has a son of her own, unbeknownst to Nancy. And ultimately she makes sacrifices with results that neither woman could have foreseen. The tragedy arises not just because of their class and racial differences, and certainly not because of cruel intentions, but because both are trapped in a system where women often need to choose between working and raising their children. The peripheral characters here are hilarious because they're so stereotypical, but the complex central figures are extremely empathetic: Cheryl Graeff as Nancy and Sandra Marquez as Ana offer nuanced portrayals of mothers who are both trying to do the right thing. As their stressed-out, frustrated husbands, Thomas Gebbia and Joe Minoso are playful and fully rounded. Through 5/22: Thu-Fri 8 PM, Sat 5 and 8:30 PM, Sun 3 PM. American Theater Company, 1909 W. Byron, 773-929-1031. $25-$30.