I´ve just read this:
When Parents Kill
Why fathers do it. Why mothers do it.
Women do not, by and large, make terrific criminals. In the United States, women commit only two crimes as frequently as men. The first is shoplifting. The second is the murder of their own children. Andrea Yates, the Houston mother whose trial for the murders of three of her children ends today, and Marilyn Lemak, the Chicago nurse recently convicted of killing her three children, are not at all statistical anomalies. Somehow, womenwho commit less than 13 percent of all violent crimes in the United Statescommit about 50 percent of all parental murders.
The Numbers
Children under the age of 5 in the United States are more likely to be killed by their parents than anyone else. Contrary to popular mythology, they are rarely killed by a sex-crazed stranger. FBI crime statistics show that in 1999 parents were responsible for 57 percent of these murders, with family friends and acquaintances accounting for another 30 percent and other family members accounting for 8 percent. Crime statistics further reveal that of the children under 5 killed from 1976 to 1999, 30 percent were murdered by their mothers while 31 percent were killed by their fathers. And while the strangers, acquaintances, and other family members who kill children skew heavily toward males (as does the entire class of murderers), children are as likely to be murdered by their fathers as by their mothers.
The Murders
Perhaps more revealing than the differences in why they kill their offspring are the differences between how fathers and mothers do so. For one thing, parental murderers tend to be highly physical. According to a 1988 survey done by the U.S. Justice Department, while 61 percent of all murder defendants used a gun in 1988, only 20 percent of the parents who killed their children used one. Children were drowned and shaken, beaten, poisoned, stabbed, and suffocated. These methods betray a certain "craziness" in both gendersthey betray an intense passion and a lack of planning. But a study by the National Center for Missing and Exploited Children shows that fathers are far more violent. And mothers frequently dispose of the corpses in what researchers call a "womblike" fashion. Bodies are swaddled, submerged in water, or wrapped in plastic. Moreover, the NCMEC study showed that while the victims of maternal killings are almost always found either in or close to the home, fathers will, on average, dispose of the bodies hundreds of miles away. All these behaviors suggest that women associate these murders with themselves, their homes, and their bodies