As was discussed in the monograph, “Marijuana: The Effects on Pregnancy, the Fetus and the Newborn” [1], there is conflicting evidence regarding the interaction between cannabinoids and dopamine and variable outcomes in the neonatal period.

Dopamine is used often in the NICU to increase cardiac output and blood pressure in neonates that are acutely ill. Dopamine is a catecholamine and as a short plasma half-life of approximately two minutes. It is interesting that the effect on the neonate is dosed dependent. In low doses (<2mcg/kg/min) vasodilation occurs as specific dopamine receptors are stimulated. In a moderate dose (2-10mcg/kg/min) there is additional stimulation of beta 1-adrenergic receptors which can result in improved cardiac contractility. If a higher dose is used (>10mcg/kg/min) alpha-adrenergic receptors become involved and there is an increase in vasoconstriction and peripheral resistance. This dose dependency pathophysiology only increases the complex interactions which make it difficult to predict neonatal effects.

Studies have demonstrated that short term maternal marijuana use increases dopamine production in the newborn. However, with long term, chronic usage, the dopamine system is inhibited and thee are decreased levels in the newborn.

Because of the many interactions of marijuana, I would have expected that there would be an acute marijuana intoxication syndrome. However, unlike opioids, there is no clinical description of an “acute withdrawal effect”. I strongly believe that with the increasing use of synthetic cannabinoids (fake weed) there will be reports of an acute intoxication syndrome.

There has been a report of a neonatal death due to marijuana toxicity [2] where there was extensive necrosis and hemorrhage noted pathologically in the liver and adrenal glands.

I have only focused on the interactions of cannabinoids and dopamine. As mentioned in the original manuscript cannabinoid signaling is necessary for “pre-implementation development, uterine receptivity during implantation and fallopian tube function which is responsible as the fertilized egg flows into the uterus”. There are cannabinoid receptors (CB1, CB2) that are present in the placental and many neonate organs. These receptors are involved with transmitters in the central nervous system. In addition, there is increasing evidence that fetal brain development is affected by cannabinoid exposure.

Variable outcomes, conflicting clinical results and inconsistency add to the confusion. The American College of Obstetrics and Gynecology discourages the use of marijuana during pregnancy. The American Academy of Pediatrics recommend that pregnant women avoid marijuana use.

I believe the only predictable outcome is that marijuana use in pregnancy and therefore the effects on the newborn will continue to increase in the future. Legalization, increasing availability and a large number of cannabinoids containing products will lead to these effects on the newborn.