Debunking the myths about cannabis use during pregnancy – How cannabis can endanger the unborn child


The use of cannabis has increased over the past decades and with it the need to educate pregnant women about the adverse effects of cannabis use during pregnancy. A cohort study from Spain analysed data from the last 10 years to investigate the exact impact of cannabis use during pregnancy and how women can be encouraged to stop using it when pregnant. The data clearly warns expectant mothers against consuming cannabis, as there is a significant risk of preterm birth, low birth weight, and other complications. However, identifying women who are in the early stages of their pregnancy and use cannabis and offering them conselling to encourage them to quit has proven to be successful.

The most commonly used illicit drug by women of childbearing age is cannabis, and use often continues into pregnancy. This makes cannabis the most frequently used illegal drug among pregnant women. Statistics show that cannabis use has been steadily increasing in recent years and is being decriminalised and legalised in more and more countries. However, it seems that the vast majority of pregnant women know only little about the effects of cannabis use during pregnancy.

For this reason, a study conducted at the Hospital Universitari Vall d’Hebrón in Barcelona, Spain investigated what it takes for women to discontinue their use during pregnancy and what consequences this can have for the foetus. To date, cannabis consumption for private use has been decriminalised in Spain and the country, with 9% of the population, has one of the highest prevalence rates of cannabis consumption in Europe. It is estimated that half of cannabis users continue their use during pregnancy. The researchers thus asked pregnant women to either self-report their consumption or voluntarily take a urine test. A total of 142 women were included in the study, of which almost 75% continued their drug intake throughout pregnancy.


Cannabis use during pregnancy is a great risk to the infant’s health

The study shows that women who used cannabis throughout their entire pregnancy had a higher risk of preterm birth and low birth weight, were more likely to be admitted to a neonatal intensive care unit (NICU) or special care baby unit (SCBU), and were discharged from hospital significantly later. In addition, these women often had to bottle feed their newborn afterwards. After birth, urine tests were taken on the newborns, revealing that Tetrahidrocannabinol (THC), the psychoactive constituent of cannabis, was detected in almost 40% of neonates, if the mother had chosen to continue the use.

There may be uncertainty in the general population about the effects of cannabis use during pregnancy due to discrepancies in literature, insufficient counselling of parents by healthcare providers, and the promotion of the drug by cannabis retailers as safe, natural, and effective to mitigate pregnancy symptoms.


Early detection of cannabis use increases the likelihood for discontinuation

The study also identified factors that support interventions to encourage pregnant women to quite using cannabis. The earlier the use was discovered, the more successful it was to convince the expectant mother to stop. In addition, referral to mental health specialists for cannabis cessation helped mothers to quit and not relapse. Further, some mothers stop using in their third trimester because they fear neonatal complications and do not want to activate child protection service protocols related to cannabis use.

The study concludes with recommendations to promote access to cannabis cessation and motivational interventions, better coordination between obstetric and healthcare social workers, and early detection of use through screening methods as the most influencable factors for discontinuation. The research team emphasised that the expectant mothers valued open communication with obstetricians who acknowledge their motivations for cannabis use and are open to information about possible risks. However, not all mothers felt comfortable discussing the topic with their doctor and might be better addressed through information material provided by healthcare providers.


Paper available at:

Ful list of authors: Maia Brik, Miguel Sandonis, Carmen Cabeza Oliver, Joaquín Temprado, Alina Hernández Fleury, Elena Sánchez Echevarria, Elena Carreras


More information and access to counselling: