Every eight seconds, a baby is born in the United States, and almost as often—every 17 seconds on the average—someone purchases an item from Workman's What to Expect series of pregnancy and child-rearing guides.

This month marks the first new arrival to the series in 10 years, The What to Expect Baby-Sitter's Handbook, with a 100,000-copy first printing. In addition to tips on bottlefeeding, lyrics for classic songs like "The Itsy-Bitsy Spider," and advice on what to do if children are caught naked together, choke or become injured, the $12.95 wirebound paperback includes plenty of space for personalized notes. "It's a Cliffs Notes version of the What to Expect books," said Heidi Murkoff, who, with Sharon Mazel, wrote the guide for parents seeking a one-volume resource to give to their babysitters.

"Because of the strength of the series, it will sell better than any other baby-sitter book," predicted Thea Kotroba, buyer for the two Chester County Book and Music Company stores in West Chester and Downington, Pa. However, she noted, none of the other titles in the series have surpassed the sales of What to Expect When You're Expecting (1984) by Murkoff, her late mother, Arlene Eisenberg, and her sister, Sandee Hathaway. That title is currently in its third edition with a total of 12 million copies in print.

The second book in the series, What to Expect the First Year (1989), is the runner-up, with 7.2 million copies in print, including the revised version published last October. Murkoff will go on a 20-city tour in February to promote the new edition— which tackles up-to-the-minute topics such as overseas adoption and "nanny cams"—along with the new babysitting book.

"What to Expect is a great brand," commented Daniel Goldin, buyer for the five Harry W. Schwartz Bookshops in the Milwaukee, Wisc., area, who sees little risk of the series becoming overpublished now that there are a total of seven books, a wall planner and a gift set that pairs the two most popular titles. "It's no Chicken Soup," he said. "They haven't done a lot of licensing the way other people have."

That's not to say that Murkoff is putting up her feet. She's authored nine children's books for HarperCollins, including What to Expect When You Use the Potty (Jan.). And five years ago she created the What to Expect Foundation (www.whattoexpect.org) with Eisenberg and Lisa Bernstein, who used to publicize the books at Workman and now serves as the foundation's executive director. The organization, dedicated to literacy and healthcare support, publishes a spiral-bound prenatal guide, Baby Basics, that addresses the needs of low-income families.

"We knew we were reaching the vast majority of book-buying moms with the series," said Murkoff, "but that left out a huge segment of the pregnant population." In addition to physical development, Baby Basics covers issues such as navigating Medicaid. Close to 150,000 free copies (in English and Spanish, with Chinese and Portuguese editions in the pipeline) have been distributed via doctors' offices.

Meanwhile, a second edition of What to Eat When You're Expecting is planned for September, and Murkoff is writing a new book covering the ages from five to 10. After that, she plans to undertake a guide for parents of teenagers. "That's probably the most requested What to Expect book," she reported. "People correctly perceive that it's the most challenging phase of child-rearing after the toddler years. Actually, a lot of the same strategies work with toddlers and teenagers, although one's bigger than you and has the keys to the car."