A prospective study on intrauterine cannabis exposure and fetal blood flow

Background: Cannabis is commonly used among pregnant women. It is unclear whether cannabis exposure causes hemodynamic modifications in the fetus, like tobacco does.
Aims: This study aims to ascertain fetal blood redistribution due to intrauterine cannabis exposure.
Methods: This study was embedded in the Generation R Focus Study, a population-based cohort of parents and children followed from pregnancy onwards. In late pregnancy, fetal hemodynamics was assessed with ultrasound measurements in cannabis-exposed and non-exposed fetuses. Pregnant women reported about substance use during pregnancy. A distinction was made between continued cannabis use (n = 9), cannabis use only in early pregnancy (n = 14), continued tobacco use (n = 85), tobacco use only in early pregnancy (n = 92), and no tobacco or cannabis use during pregnancy (n = 85).
Results: Continued cannabis use was associated with an increased pulsatility and resistance index of the uterine artery, while discontinued cannabis use was associated with a decreased pulsatility, and resistance index, as compared to controls. Additionally, continued cannabis exposure resulted in a significantly higher uterine pulsatility index and uterine resistance index compared to tobacco exposure. Continued cannabis use was found to be associated with a smaller aortic diameter, as well. No association between intrauterine cannabis exposure and the fetal cerebral vascular system was found.
Conclusions: Our findings suggest that intrauterine cannabis exposure was associated with changes in hemodynamic programming of the vascular system of the fetus in late pregnancy mainly due to tobacco exposure, but intrauterine cannabis exposure did demonstrate a specific effect on the uterine blood flow.