Analysis reaffirms there is ‘no safe level of cigarettes’ before, during pregnancy

Key takeaways:

• Study results show an association between smoking before or during pregnancy and severe neonatal morbidity.
• Researchers observed increased odds for severe neonatal morbidity at all levels of smoking intensity.

Even one or two cigarettes a day before or during pregnancy can increase the risk for several health complications in newborns, study results published in the Journal of Epidemiology & Community Health showed.

The findings “re-emphasize the need to prevent smoking initiation for non-smokers and to promote smoking cessation for smokers,” the researchers wrote.

Healio previously reported that children of mothers who snuffed or smoked during pregnancy had higher risks for sudden unexpected infant death and postneonatal mortality.

“However, only a few studies have assessed the association between maternal cigarette smoking and infant [severe neonatal morbidity (SNM)], with conflicting findings,” Lili Yang, from Cheeloo College of Medicine at Shandong University in China, and colleagues wrote. “Neurodevelopmental impairments related to infant SNM may persist into childhood and adulthood. Thus, it is important to understand better the modifiable risk factors associated with infant SNM.”

The population-based cohort study examined U.S. national birth certificate data from 2016 to 2019. The study sample included12,150,535women aged 18 to 49 years who had single-child births.

Researchers classified smoking intensity as one to two, three to five, six to nine, 10 to 19 or more than 20 cigarettes a day.

Meanwhile, they defined SNM as assisted ventilation immediately following delivery, neonatal intensive care unit (NICU) admission for continuous mechanical ventilation, suspected neonatal sepsis or seizure or serious neurologic dysfunction.

Among the study cohort, 9.3% reported smoking cigarettes before pregnancy. The proportion of reported smokers decreased gradually during pregnancy, starting with 7% in the first trimester, falling to 6% during the second and an additional slight downtick to 5.7% during the third

The researchers reported the following adjusted ORs for SNM among newborns based on the mother’s smoking intensity before pregnancy compared with non-smokers:

• 1 to 2 cigarettes per day: 1.16 (95% CI, 1.13-1.19);
• 3 to 5 cigarettes per day: 1.22 (95% CI, 1.2-1.24);
• 6 to 9 cigarettes per day: 1.26 (95% CI, 1.23-1.29);
• 10 to 19 cigarettes per day: 1.27 (95% CI, 1.25-1.28); and
• 20 or more cigarettes per day: 1.31 (95% CI, 1.3-1.33)

The analysis also linked maternal smoking to individual SNM components, including infant NICU admission at all pre-pregnancy smoking levels in the analysis.

Yang and colleagues also pointed out that women who only smoked before pregnancy or only during the first, second or third trimester still had a greater risk for SNM compared with women who never smoked before or during pregnancy.

The researchers reported two notable study limitations, including a lack of data that prohibited evaluation of any association between exposure to secondhand smoke and SNM, in addition to self-reported maternal smoking information.

“Overall, these data suggest that there is no safe period and no safe level of cigarettes consumed shortly before or during pregnancy,” they wrote.

Because of the high prevalence of maternal smoking before and during pregnancy found in the study, Yang and colleagues advised that stronger tobacco control policies “such as strict national tobacco control laws and higher adherence to the WHO Framework Convention on Tobacco Control,” be implemented in the United States.

References:

• Just 1-2 cigarettes/day before or during pregnancy linked to major newborn health problems. Available at: https://bmjgroup.com/just-1-2-cigarettes-day-before-or-during-pregnancy-linked-to-major-newborn-health-problems. Published Aug. 21, 2024. Accessed Sept. 6, 2024.
• Yang L, et al. J Epidemiol Community Health. 2024;doi:10.1136/jech-2024-222259.