According to a new study, smoking tobacco or marijuana as well as the use of illegal drugs increases the risk of a stillbirth. The study was published in the January 2013 edition of the journal Obstetrics & Gynecology by the Stillbirth Collaborative Research Network.
The study authors note that during the second half of the 20th Century, a sharp decrease in perinatal mortality (fetal death) occurred in the US. During this period, the US perinatal mortality rated gradually dropped from 18 per 1,000 births in 1950 to 6.05 per 1,000 births in 2006. However, despite this decrease, the US stillbirth rate is currently significantly higher than that of many other developed nations; it affects almost 26,000 neonates per year. The investigators explain that smoking and drug abuse during pregnancy can be modifiable risk factors for stillbirth; however, the relationship between smoking and/or illegal drugs and stillbirth is primarily based on studies that are based on self-reporting of smoking and drug abuse. Therefore, they conducted a study to assess the association of smoking and illicit drug use with stillbirth by measuring metabolites in maternal blood and umbilical cord blood in deliveries complicated by stillbirth. They compared these measurements with those from live births.
From March 2006 through September 2008, the researchers evaluated more than 90% of deliveries to residents of five diverse geographical areas in the US. They attempted to include all stillbirths and live-born controls. Umbilical cord samples from stillborn infants and live births were collected and frozen for subsequent analysis. Maternal blood was drawn at delivery and analyzed for cotinine. Cotinine is a metabolite of nicotine; thus, it measures tobacco use.
A total of 663 stillbirth deliveries were evaluated; among that group, 418 (63%) had cord blood analysis and 579 (87%) had maternal cotinine analysis performed. Among 1,932 live birth deliveries, 1,050 (54%) had cord blood analysis and 1,545 (80%) had maternal cotinine analysis. The researchers found that a positive cord blood analysis for any illicit drug was associated with stillbirth (1.94-fold increased risk). The most common individual drug was cannabis; however, the results were skewed by cotinine being also present. The researchers found that both maternal self-reported smoking history and maternal serum cotinine levels were associated in a dose–response relationship with stillbirth. They also measured the effect of second-hand smoke. Women who denied smoking and had cotinine present in their blood also were more likely to have delivered a stillborn infant.
The study authors concluded that cannabis use, smoking, illegal drug use, and exposure to second-hand smoke, separately or in combination, during pregnancy increased the risk of stillbirth. They noted that cannabis use will likely escalate because of increased legalization of the drug, more women will suffer the tragedy of a stillbirth.
The Stillbirth Collaborative Research Network includes the University of Utah School of Medicine (Salt Lake City, Utah), Emory University and Emory University School of Medicine (Atlanta, Georgia), the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda (Maryland), RTI International, Research (Triangle Park, North Carolina). Columbia University (New York, New York), the University of Texas Medical Branch at Galveston (Galveston, Texas, Zhe University of Texas Health Science Center at San Antonio (San Antonio, Texas), and Brown University School of Medicine (Providence, Rhode Island).