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Cocaine and tobacco use during early pregnancy substantially increases the risk of miscarriage

Women who smoke early in their pregnancies have nearly twice the risk of having a miscarriage as women who don't smoke. Pregnant women who use cocaine also substantially increase their risk of miscarriage. In fact, a new study estimates that cocaine use and smoking together accounted for 24 percent of the miscarriages suffered by a group of predominantly poor and black adolescents and women. The study was supported in part by the Agency for Health Care Policy and Research (HS08358) and led by University of Pittsburgh researcher Roberta B. Ness, M.D., M.P.H. Dr. Ness is lead investigator of the AHCPR-supported Pelvic Inflammatory Disease Patient Outcomes Research Team (PORT).

Dr. Ness and her colleagues examined the association between cocaine and tobacco use and miscarriage (spontaneous abortion) among 970 pregnant adolescents and women (14 to 40 years) who sought care at an urban emergency department. They used women's self-reports and urinalysis to detect tobacco and cocaine use and additional hair analysis to detect cocaine use. Both nicotine and cocaine are vasoconstrictors that reduce uterine and placental blood flow, which may be related to miscarriage.

Among those who had miscarriages either at study entry or up to 22 weeks gestation, 29 percent used cocaine (hair analysis) and 35 percent smoked (urinalysis), compared with 21 percent (cocaine use) and 22 percent (tobacco use) of adolescents and women who did not have miscarriages. The presence of a nicotine metabolite, cotinine, in urine was associated with nearly twice the risk (odds ratio [OR] of 1.8; 1 is equal) of miscarriage. The presence of cocaine in hair samples (but not as measured by self-report or urinalysis) was independently associated with an increase in miscarriage (OR of 1.4), after controlling for demographic and drug-use factors. Hair analysis is an extremely sensitive marker of cocaine use over a period of weeks or months, depending on the length of hair analyzed. However, serum and urine tests only detect cocaine use within 72 hours of testing, so that intermittent use may not be detected.

More details are in "Cocaine and tobacco use and the risk of spontaneous abortion," by Dr. Ness, Jeane Ann Grisso, M.D., Nancy Hirschinger, M.A., and others, in the February 2, 1999, New England Journal of Medicine 340(5), pp. 333-339.

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