Number of THC-exposed newborns at Michigan hospital increases after recreational weed legalized

Researchers out of Michigan say it looks like legalizing weed may lead to greater cannabis use, which means that more pregnant women who smoke could be exposing their developing babies to THC.

There was a 32.5 per cent increase in THC-exposed newborns at a Michigan hospital between 2018 and 2019, following legalization of recreational weed in late 2018, according to Healio. The findings were presented recently at the American Academy of Pediatrics National Conference & Exhibition.

In all, 320 newborns born in the hospital between January 2014 and January 2020 tested positive for THC in their meconium, Healio reports. But the findings also indicate a steady rise in the rate of THC in meconium dating back to 2015.

While traces of THC were detected in five per 1,000 live births at the hospital in 2014, that increased annually after 2015. That year, the rate was 4.9, while it was 5.5 in 2016, 6.8 in 2017, 8.0 in 2018 and 10.6 per cent in 2019.

Although positive tests doubled over the 2014 to 2019 period, Healio points out, the biggest hike occurred from 2018 to 2019, representing the first year after legalization of recreational weed.

Earlier this year, MLive.com reported that warning labels for pregnant women were coming to Michigan. The warning for both medicinal and recreational cannabis products read: Use by pregnant or breastfeeding women, or women planning to become pregnant, may result in foetal injury, preterm birth, low birth weight or developmental problems for the child.

The U.S. Food and Drug Administration (FDA), for its part, “strongly advises against” using CBD, THC and “marijuana in any form during pregnancy or while breastfeeding.”

If Twitter is any indication at all, questions about maternal marijuana use and infant health is of interest. / Photo: Getty Images/iStock Photo Getty Images/iStock Photo

If pregnant women are more likely to smoke cannabis, “this is important because long-term studies show that in utero THC exposure leads to impaired neurodevelopment, leading to problems with memory, attention and cognition,” Dr. Allek Scheele told Healio.

If Twitter is any indication at all, questions about the link between maternal marijuana use and infant health is of interest. A study published in 2018 explored the types of messages disseminated on Twitter about marijuana use and infant and maternal health.

Accounting for tweets from 2006 through April 2017, 550 were captured. The most common health outcomes associated with prenatal marijuana exposure were: poor brain development (27.3 per cent), inadequate development of the nervous system (23.6 per cent), low birth weight (23.3 per cent), poor behavioural outcomes (21.0 per cent) and infant memory issues (19.3 per cent).

Research regarding how cannabis consumption by a pregnant or breastfeeding mother can influence the health of a child has been uneven.

A study published back in 2010 found that women who had been smoking cannabis and became pregnant quit or reduced their consumption as pregnancy progressed. / Photo: cheonlijyang / iStock / Getty Images Plus cheonlijyang / iStock / Getty Images Plus

Just this month, a position statement from the National Association of Neonatal Nurses advised pregnant and breastfeeding mothers to abstain from using cannabis. The group cited a lack of safety data around maternal consumption, transmission to breast milk and potential impact on infants.

This summer, a Canadian study identified an association between weed use while pregnant and the incidence of autism spectrum disorder in offspring.

And a study published back in 2010 found that women who had been smoking cannabis and became pregnant quit or reduced their consumption as pregnancy progressed, although “positive maternal oral fluid tests cast doubt on the veracity of some maternal self-reports.” Researchers found that cannabis exposure was “associated with decreased birth weight, reduced length and smaller head circumference, even after data were controlled for tobacco co-exposure.”

All that said, a recent review of decades of studies involving marijuana and pregnant women found that evidence does not suggest an association between prenatal cannabis exposure alone and clinically significant cognitive functioning impairments. “Fewer than five per cent of studies exploring the issue showed any statistical difference between children’s scores on cognitive tests, whether better or worse,” according to Forbes.