When the first instruction about bathing the baby turned out to be taking off my wristwatch, I threw the book away,"" said one intelligent mother about a popular child-rearing book. This isn't like that. Beck covers the gamut of problems from diaper rash to sex education, backing up her theory with scientific studies. In the chapter entitled ""Is Your Baby Developing Normally,"" for example, she includes detailed information designed to reassure even the most panicked mother: balancing on one foot--25% by 2.6 years, 90% by 4.3 years; smiling--25% by 1.4 months, 90% by 5 months. Apart from doling out advice about how to get a youngster into bed without a fight (maybe his bedtime needs reevaluating), she's careful to say that nothing works with children all the time, that child rearing is an imprecise art at best, and the safest way to proceed is not to worry. This is a primer to grab when the baby comes home from the hospital and to clutch until the child is about ten.