PITTSBURGH, Feb. 3 -- Tobacco smoking and cocaine use independently contribute to spontaneous abortion (miscarriage), according to results of a landmark study led by Roberta B. Ness, M.D., M.P.H., at the University of Pittsburgh Graduate School of Public Health (GSPH). Results are reported in the February 4 issue of The New England Journal of Medicine.
"This is the first study to show that cocaine use is linked with subsequent risk of miscarriage and that cocaine use is associated with miscarriage independent of tobacco use," said Dr. Ness, associate professor of epidemiology, director of the Cancer Epidemiology Program of the University of Pittsburgh Cancer Institute and director of the Epidemiology of Women's Health Program at the GSPH.
"This research emphasizes that virtually any exposure to illicit drugs is dangerous for a pregnant woman and her fetus," said Alan I. Leshner, M.D., director of the National Institute on Drug Abuse (NIDA), National Institutes of Health, which provided partial funding for the study. "With addiction, an individual's compulsion to use drugs may well be greater than her ability to protect her health and pregnancy. The need for adequate treatment for these women is critical."
The rates of substance use were high in the study group of 970 inner-city, pregnant women of lower socioeconomic status. The report is based on 400 of those women who had miscarriages (cases) and 570 who carried their pregnancies past 22 weeks (controls). Almost 30 percent had evidence of cocaine use in the previous few months, and over one-third currently smoked. Both current smoking and cocaine use significantly increased the risk of miscarriage. In fact, the study reports that 24 percent of the risk for miscarriage in study women could be related to cocaine and tobacco use.
"Cocaine has been previously associated with low birthweight," said Dr. Ness. "Our findings suggest that it and tobacco can interfere with pregnancy, and that they act early in gestation."
According to the study report, cocaine was measured at baseline by self-report and urine and by hair analysis. Tobacco use was measured by self-report and urine cotinine, a major metabolite of nicotine. Hair analysis for cocaine was chosen because it serves as an indicator of long-time use. Hair samples were washed thoroughly before measurement to reduce the incidence of false positives due to external contamination.
"Tobacco use is, perhaps, the greatest environmental contributor to neonatal health problems," said Dr. Ness. "Young women are also the fastest growing population to take up smoking. For both these reasons, it is vitally important that we tackle the problem of tobacco use during pregnancy. Ongoing research is evaluating the effectiveness of smoking cessation programs during pregnancy. Evaluation and implementation of such programs should be a priority.
"The use of cocaine," she continued, "probably varies substantially over different populations. In one national survey, five percent of women of childbearing age reported cocaine use in the past month. Marital status is associated with reduced use, and young age is associated with increased use. The rates in our study are particularly high, probably because they reflect inner-city, indigent, young, unmarried women."
Dr. Ness specializes in reproductive and women's health. She has additional research interests in obesity, cardiovascular disease and pelvic inflammatory disease.
Celebrating its 50th year, the GSPH is world-renowned for contributions that have influenced public health practices and medical care for millions of people. For more information about the GSPH access http://www.pitt.edu/~gsphhome/.
This research is supported by grants from the National Institute on Drug Abuse and the Agency on Health Care Policy Research.
Journal
New England Journal of Medicine