Only about half of women with high nicotine levels during the last days of their pregnancies reported that they were still smoking cigarettes in a newly reported study, suggesting that smoking prevalence during pregnancy may be higher than believed.
While 8.6% of the women in the retrospective, single-center study acknowledged smoking cigarettes late in their pregnancies, 16.5% had high-level nicotine exposure detected through mass spectrometry screening, and an additional 7.5% had low-level nicotine readings, indicative of second-hand smoke exposure.
Laboratory-recorded nicotine exposures were higher than reported smoking rates among African American women (7.9% versus 21.1%), white women (9.5% versus 15.7%), and women living in poverty (15.8% versus 30.7%), James M. Greenberg, MD, of Cincinnati Children's Hospital Medical Center, and colleagues, wrote online in the Journal of Perinatology.
In an interview with MedPage Today, Greenberg said the disparity between self-reported cigarette smoking and nicotine exposure rates does not necessarily indicate that the women lied when asked about their smoking status: "I don't really get the sense that this is the case," he said. "The findings may partly reflect a certain amount of wishful thinking or a misinterpretation of the question. We also have no idea how many women used e-cigarettes, which deliver nicotine, but not the carbon monoxide and other chemicals found in cigarettes."
Cigarette smoking during pregnancy is associated with a higher risk for low-birth weight delivery, stillbirth, and infant death, with nicotine exposure alone associated with increases in vasoconstriction and possibly fetal growth restriction.
While the prevalence of cigarette smoking during pregnancy is reported to be around 10%, the prevalence of nicotine- and secondhand smoke exposures are not well understood, Greenberg and colleagues wrote.
Their study focused on nicotine exposures during the last few days of pregnancy, measured through mass spectrometry analysis of urine cotinine levels. Cotinine is a metabolized byproduct of nicotine exposure with a reported half-life of 8 to 16 hours. Mass spectrometry was also used to measure other drug exposures.
Women delivering at Cincinnati Children's and surrounding hospitals are routinely tested for drug use in order to facilitate timely identification and treatment of infants at risk for opioid withdrawal. As a result, the researchers were able to obtain mass spectrometry laboratory data of urine measures of cotinine, opioids, and other drugs.
The study cohort included 787 women who delivered a live infant during an 18-month period (March 2014 to August 2015) at Cincinnati Children's. The mixed urban-suburban population was 76.8% non-Hispanic white, 17.9% black, and 5.3% other races; and 61% and 36.4%, respectively, were privately and Medicaid-insured.
A total of 68 women (8.6%) self-reported any amount of cigarette smoking during the final trimester of pregnancy, while 117 (16.5%) tested positive for high-level nicotine exposure; 53 women (7.5%) tested positive for low-level nicotine exposure; and 708 women had laboratory-tested samples.
Women with positive nicotine exposures were much more likely to test positive for other drug exposures, especially cannabinoid, opioid, and polypharmacy exposures, suggesting that testing nicotine exposure may help facilitate identification of other drug exposure.
"We identified a relationship between high- and low-level nicotine exposures and other drug exposures that also have an important role in mediating perinatal outcomes," the researchers wrote. "Thus, there remains a critical need for improved measurement of nicotine exposures throughout pregnancy, which capture primary as well as passive exposures from all potential sources."
The single-center design of the trial was cited by the researchers as a potential study limitation.
Greenberg said additional research will be needed to develop a comprehensive picture of nicotine exposure during pregnancy and to better understand the impact of nicotine exposure on fetal outcomes in women who use e-cigarettes or other nicotine-only delivery devices.
He added that the use of nicotine-replacement therapy for smoking cessation during pregnancy remains controversial.
"Some obstetricians say 'no way,' and some believe nicotine-replacement therapy represents the best way to get a pregnant patient to quit smoking," he said.
The research was supported by the Cincinnati Children's Hospital and the Amgis Foundation.
The researchers reported having no relevant relationships with industry related to the study.
- Reviewed by F. Perry Wilson, MD, MSCE Assistant Professor, Section of Nephrology, Yale School of Medicine and Dorothy Caputo, MA, BSN, RN, Nurse Planner