Reduced fetal cerebral blood flow following prenatal drug exposure predicts perinatal mortality

Abstract Background Children exposed prenatally to alcohol or cannabinoids individually can exhibit growth deficits and increased risk for adverse birth outcomes. However, these drugs are often co-consumed and their combined effects on early brain development are virtually unknown. The blood vessels of the fetal brain emerge and mature during the neurogenic period to support nutritional needs of the rapidly growing brain. Teratogenic exposure during this gestational window may therefore impair fetal cerebrovascular development. Objective To determine whether prenatal polysubstance exposure confers additional risk for impaired fetal-directed blood flow and offspring viability compared to each drug individually. Study Design We performed high resolution in vivo ultrasound imaging in C57Bl/6J pregnant mice. After pregnancy confirmation, dams ( n =40) were randomly assigned to one of four groups: drug-free control, alcohol-exposed, cannabinoid-exposed or alcohol-and-cannabinoid-exposed. Drug exposure occurred daily between Gestational Days 12-15, equivalent to the transition between the first and second trimesters in humans. Dams first received an intraperitoneal injection of either cannabinoid agonist CP-55940 (750µg/kg) or volume-equivalent vehicle. Then, dams were placed in vapor chambers for 30min of inhalation of either ethanol or room air. Dams underwent ultrasound imaging on three days of pregnancy: Gestational Day 11 (pre-exposure), Gestational Day 13.5 (peri-exposure) and Gestational Day (post-exposure), and were subsequently monitored for health and delivery outcomes. Results Of all exposure groups, only dams co-exposed to both alcohol and cannabinoids experienced reduced gestational weight gain while undergoing drug treatments. These same co-exposed pregnant mice also demonstrated higher (+42mg/dL) blood ethanol concentrations than dams exposed to alcohol only. All drug exposures decreased fetal cranial blood flow 24-hours after the final exposure episode, though combined alcohol and cannabinoid reduced internal carotid artery blood flow relative to all other exposures. Umbilical artery metrics were not affected by drug exposure, indicating a specific vulnerability of fetal cranial circulation. Cannabinoid exposure significantly reduced cerebroplacental ratios, mirroring prior findings in marijuana-exposed human fetuses. Post-exposure cerebroplacental ratios significantly predicted subsequent perinatal mortality ( p =0.019, area under the curve, 0.772; sensitivity, 81%; specificity, 85.70%) and retroactively diagnosed prior drug exposure ( p =0.005; AUC, 0.861; sensitivity, 86.40%; specificity, 66.7%). Conclusion(s) Fetal cerebrovasculature is significantly impaired by exposure to alcohol or cannabinoids, and co-exposure confers additional risk for adverse birth outcomes. Considering the rising potency and global availability of cannabis products, there is an imperative for research to explore translational models of prenatal drug exposure, including polysubstance models, to inform appropriate strategies for treatment and care in pregnancies affected by drug exposure. Key Points Question Does simultaneous prenatal exposure to alcohol and cannabinoids present significant additional risk to fetal health compared to each drug individually? Findings Maternal murine ultrasound analyses showed that alcohol and cannabinoid exposure, individually, reduced fetal cerebral arterial blood flow metrics. Notably, polysubstance-exposed fetuses demonstrate the worst cerebral hemodynamics, and reductions in fetal blood flow significantly predict subsequent perinatal offspring mortality. Meaning Prenatal drug exposure persistently reduces fetal-directed blood flow, which can disrupt normal embryonic growth and neural development, and polysubstance exposure augments deficits specifically in cerebral arterial blood flow.