In a case that shocked the nation, Amy Grossberg and Brian Peterson, high school sweethearts from affluent New Jersey families, went to prison Thursday for contributing to the death of their newborn infant in a Newark motel room in 1996. Grossberg was sentenced to two and a half years, while Peterson received a lesser sentence of two years because, said Superior Court Judge Henry Ridgely, he pleaded with Grossberg to seek help with the pregnancy. Both defendants could have received 10 years. Sobbing in court, Grossberg said, "I'll never be able to forgive myself for what happened." Today is her 20th birthday.