The Baby Book weaves together three elements - a historical sketch of American life and culture in the twentieth century through the news of the New York Times, a history of the Children's Bureau, and the advice given to parents through the publication of the Bureau's pamphlet Infant Care. William Kessen focuses on the period from 1914 to 1989, a time of major shifts in child rearing practices.

The book highlights the place of women in society, the diversity and variety of American babies and their families, and who are the important decision makers in an infant's life. Each chapter begins with a reflection on American and world events, relying chiefly on reporting in the New York Times.

Then follows the history of the Children's Bureau, established in 1912 by President Taft to focus on the well-being of children and their families. The final section of each chapter, and the heart of the matter, is the evolving narrative of Infant Care and its advice to (primarily) mothers on how to care for their infants; from what to feed them, advice on play and toileting and clothing, schedules and sickness and advice from physicians and psychologists over the years.

. .