December 16, 2013

Tobacco, Drug Use May Raise Risk of Stillbirth

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Smoking tobacco or marijuana, taking prescription painkillers, or using illegal drugs during pregnancy may increase the risk of stillbirth, according to a new study.

Stillbirth occurs when a fetus dies at or after 20 weeks of gestation. While the U.S. stillbirth rate decreased from 18 per 1,000 births in 1950 to 6 per 1,000 births in 2006, it still remains higher than many other developed countries and affects almost 26,000 U.S. newborns each year.

To learn more about the causes and prevention of stillbirth, NIH created the Stillbirth Collaborative Research Network. With support from NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the network enrolled more than 600 women who delivered stillbirths at 59 participating hospitals. For comparison, the scientists also enrolled almost 2,000 women who gave birth to a live infant.

The researchers took umbilical cord and blood samples at delivery from the 2 groups of women. They tested the women’s blood for cotinine, a derivative of nicotine. They tested the umbilical cords for evidence of the stimulants cocaine and amphetamine; prescription painkillers, such as morphine and codeine; and marijuana. They also asked the women to self-report smoking and drug use during pregnancy. The results appeared online on December 6, 2013, in Obstetrics & Gynecology.

Among the women who experienced a stillbirth, about 19% showed traces of cotinine and about 7% tested positive for other drugs. In comparison, among women who gave birth to a live infant, about 9% tested positive for cotinine and 4% for other drugs.

Based on blood test results and the women’s responses, the researchers estimated that tobacco use increased the risk of stillbirth by 1.8 to 2.8 times, with the highest risk found among those with the highest cotinine levels. Women who reported they didn’t smoke but tested positive for cotinine (and so were presumably exposed to second-hand smoke) had roughly double the risk of stillbirth.

Women with stillbirth were twice as likely as those with a live birth to report having been addicted to an illicit drug. A positive test for any drug in the umbilical cord was also associated with about double the risk for stillbirth. However, the researchers couldn’t entirely separate the effects of smoking tobacco from those of smoking marijuana. In addition, the number of women who tested positive for stimulant or prescription painkiller use was small. Further study will be needed to understand the effects of these drugs on stillbirth.

With the legalization of marijuana in some states and the continued widespread use of other drugs, these findings highlight the need for preventing drug and tobacco use during pregnancy.

“Smoking is a known risk factor for stillbirth, but this analysis gives us a much clearer picture of the risks than before,” says senior author Dr. Uma M. Reddy of NICHD. “Additionally, results from the latest findings also showed that likely exposure to secondhand smoke can elevate the risk of stillbirth.”

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References: Association Between Stillbirth and Illicit Drug Use and Smoking During Pregnancy. Varner, Michael W. MD; Silver, Robert M. MD; Rowland Hogue, Carol J. PhD; Willinger, Marian PhD; Parker, Corette B. DrPH; Thorsten, Vanessa R. MPH; Goldenberg, Robert L. MD; Saade, George R. MD; Dudley, Donald J. MD; Coustan, Donald MD; Stoll, Barbara MD; Bukowski, Radek MD; Koch, Matthew A. MD, PhD; Conway, Deborah MD; Pinar, Halit MD; Reddy, Uma M. MD, MPH; for the Eunice Kennedy Shriver National Institute of Child Health and Human Development Stillbirth Collaborative Research Network. Obstet Gynecol. 2014;0:1–13.

Funding: NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).