``I could feel my life changing, the old familiar parts of it crumbling away and a new shape emerging.'' The narrator of Mary Grimm's ``Before,'' reflecting on her emotions as she is being wheeled into a delivery room, sounds a note repeated, with some artful variations, in many of the reprinted tales in this diverse collection: Motherhood changes everything. Another theme, succinctly rendered in Barbara Kingsolver's ``Quality Time'' (from Homeland, 1989), is that ``Parenting is something that happens mostly while you're thinking of something else.'' Most of these stories, dwelling on the complex negotiations of mothers and young children, are exact but hopeful. In ``Starlight'' (from Floating, 1984), Marian Thurm catches the delicate growth of trust and affection between a mother and her two young sons, separated by a divorce. ``Chances with Johnson,'' from White Boys and River Girls (1995) by Paula K. Gover, traces the struggles of a single mother to provide some sense of security and certainty for her son. There are several grimly downbeat works as well: A young, drug-addled mother in ``Pagan Night,'' by Kate Braverman, plots how to murder her child, and in ``King of the Sky,'' by Roxana Robinson, a battle of wills between a mother and her son culminates in tragedy. Strong stories, a startling variety of voices, and some very precise meditations on the nature of modern motherhood combine to create a unique, useful, moving anthology.