Kathy Varble of Tallahassee, Fla., is a expecting a baby at the end of this month. A baby boy, just as she and her husband wanted. The couple already has a daughter, age 4, and knew they were only going to have one more child. Although they would have been happy with either a boy or girl, they wanted to maximize their chances of it being a boy.

"My husband is the last Varble, and we really wanted to give having a boy our best shot," she says. "It wasn't something where we would have made the huge financial investment to guarantee a boy, but to try a natural method that really only required the cost of a book seemed realistic to me."

The method Varble chose to try is outlined by Dr. Mark Moore in his book Baby Girl or Baby Boy: Determining the Sex of Your Child (Washington Publishers, 2002). Co-written with his wife, Lisa, a registered nurse, it details some practices that are generally believed to increase a couple's chances of influencing the gender of their baby. While there are no guarantees, Dr. Moore estimates that, if it's followed correctly, it has a statistical probability of working 80 percent of the time.

Dr. Moore's method is based on factors such as timing of ovulation and intercourse; there are other methods that involve more medical intervention. Preimplantation genetic diagnosis is a type of in vitro fertilization (IVF) that guarantees a boy or girl, but it runs about $20,000. It also raises some difficult ethical questions, as it often results in the production of too many viable embryos that need to be dealt with in some manner.

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