Combination of cannabis and tobacco in pregnancy quadrupled infant mortality rate
American scientists conducted a retrospective population-based cohort study and found that combined tobacco and cannabis use during pregnancy was associated with significantly worse maternal and infant outcomes - much more pronounced than with either product alone. The strongest association was with infant mortality - its incidence quadrupled. The paper is reported in the journal JAMA Network Open.
As the legalization of cannabis for medical and recreational use has spread in various countries, concerns about its use during pregnancy have begun to emerge. Of particular concern is that approximately half of pregnant women combine cannabis use with tobacco smoking, and the frequency of such combined use is increasing over time. The negative effects of cannabis and tobacco use on pregnancy outcomes individually are reasonably well known, but there is very little data on the extent to which they are exacerbated when these psychoactive products are combined.
To get them, Adam Crosland of Oregon Health & Science University and colleagues analyzed data from California hospital discharge and mortality registries from Jan. 1, 2012, to Dec. 31, 2019. They included all (nearly 3.13 million) women with singleton pregnancies and a gestational age of 23-42 weeks. The average age was 29.3 years. Of these women, 0.7 percent had physician-reported cannabis use during pregnancy, 1.8 percent had tobacco use, and 0.3 percent had both; the rest were in the control group.
Over the course of the study, the prevalence of cannabis use among the participants increased from 0.5 to 1 percent, tobacco use decreased from 2.1 to 1.5 percent, and the combination of both remained stable at 0.3 to 0.4 percent. Statistical analysis of the data was performed using the χ2 criterion and multivariate Poisson regression with adjustment for demographic, socioeconomic, medical, and obstetric comorbidities.
Analysis of female outcomes demonstrated a significant increase in the incidence of hypertensive disorders in the combined use, cannabis and tobacco use alone and control group: 11.2; 12.3 and 9.6 vs. 7.6 percent (p < 0.001). The associated factor-adjusted relative risk (ARR) was 1.33; 1.36 and 1.19, respectively. The incidence of severe conditions requiring emergency care also increased in these groups: 2.6; 2.3 and 2.1 vs. 1.3 percent (p < 0.001; ARR 1.46; 1.33 and 1.42); and preterm labor: 17.5; 12.2 and 12.0 vs. 6.6 percent (p < 0.001; ARR 1.83; 1.47 and 1.48).
Infant outcomes were even worse. Infant mortality was four times higher with combined use than in the control group, 1.2 versus 0.3 percent (ARR 2.18). When cannabis and tobacco were used separately, the rate was 0.7 percent each (ARR 1.65 and 1.62). A similar trend was seen in neonatal mortality and the rate of hospitalization in the intensive care unit. Combined use also sharply increased the incidence of low birth weight babies, 18 versus 8.5 percent in the control group (ARR 1.94), and cannabis and tobacco use separately (14.3 and 13.7 percent, respectively).
Thus, co-use of cannabis and tobacco during gestation significantly increases the risks associated with each of these products to the mother and especially to the baby. This should be taken into account when counseling women and developing medical and social programs for the preparation and management of pregnancy, conclude the authors of the paper.
Previously, a Canadian study with a sample of 1.28 million births found that cannabis use during pregnancy was associated with an increased risk of preterm labor, low birth weight, underweight or overweight for gestational age, any congenital anomalies, cesarean section and gestational diabetes.