Nov. 7, 1996
Vol. 16, No. 5

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    Better way to predict pregnancy term

    New theory also identifies women at risk for preterm delivery More than a century and a half after the standard method of predicting a woman's due date was established, a new theory -- the Mittendorf-Williams Rule(TM) -- provides more accuracy in prediction, and identifies women at high risk for preterm delivery.

    The rule is named for Robert Mittendorf, Assistant Professor and Director of Health Studies in Obstetrics & Gynecology, and Michelle Williams, an epidemiologist at the University of Washington. The pair developed a computer model that uses 16 significant factors -- including maternal age, pre-pregnancy weight, race, college education, alcohol and coffee use, hypertension, and other medical conditions -- to compute a woman's due date and to determine if she is at high risk for giving birth sooner than 37 weeks gestation.

    The current due-date predictor -- Naegele's Rule -- was devised in 1838 by Franz Carl Naegele and has been used by obstetricians around the world for more than 150 years. Naegele's Rule is based on the belief that human gestation is 10 lunar cycles (nine months plus seven days), not on empirical data. A retrospective study by Mittendorf and colleagues (Obstetrics and Gynecology, 1990; Vol. 75) determined that white women with single-birth pregnancies receiving private care averaged seven days longer gestation than Naegele's Rule predicts. A second study by Mittendorf (American Journal of Obstetrics and Gynecology, 1993, Vol. 168) concluded that there are several factors -- including number of previous births, age and race -- that can be used to determine the length of pregnancy more accurately than Naegele's Rule, which does not take other factors into consideration.

    Few women deliver exactly on their due date. A prospective study comparing Naegele's Rule with the Mittendorf-Williams Rule(TM) found the latter to be twice as accurate as Naegele's Rule in predicting gestation.

    More importantly, the software can predict the likelihood of preterm delivery, which affects 400,000 births annually in the United States.

    "Until now, there has been no successful way to determine numerically the risk for preterm delivery," Mittendorf said. "By identifying these women, we may be able to lower the infant mortality rate by intensifying a woman's prenatal care, and medically manage patients differently based on this new information."

    Mittendorf-Williams Rule software for Windows(R) is currently available to physicians, hospitals and the general public for $49.95. To obtain the software on a 3.5" diskette, send name, address, where you heard about the software, and a check or money order to: Robert Mittendorf, Department of Obstetrics & Gynecology, Chicago Lying-In Hospital, MC 2050, 5841 S. Maryland Ave., Chicago, IL 60637.

    Proceeds will benefit research and patient care initiatives at Chicago Lying-In Hospital at the University of Chicago Medical Center.