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The effects of cannabis on pregnancy

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More places are legalising cannabis with growing social acceptance and anecdotal evidence of its health benefits. In some places where cannabis is legal, it is even promoted as a safe treatment for nausea and vomiting in pregnancy.

Cannabis is a general term for drugs like marijuana and other products made from the cannabis plant. It is a depressant and can cause hallucinations when consumed in high dosage. Long term use of cannabis has been linked to anxiety, depression, psychosis and other mental illnesses.

Although it is illegal to use and grow cannabis in Australia, illicit use is not uncommon. It is also estimated that half of the female cannabis users would continue to use it during pregnancy.

Alarming cannabis use in pregnancy

The 2016 Australian National Drug Strategy Household found that 10-20% of women of reproductive age had used cannabis during the preceding 12 months. Data from overseas has also shown an increase in the number of women who became pregnant while using cannabis in recent years.

Many women view marijuana as a relatively safe drug. Given the lack of information on its health consequences on pregnancy, some simply assumed that it couldn’t be too bad.

Unfortunately, cannabis is becoming more accessible and acceptable at a speed faster than research is being done. But based on current research findings, there is an urgent need to educate women on the detrimental effects of cannabis on pregnancy and fertility.

Effects on pregnancy

THC is the main psychoactive ingredient in cannabis. During pregnancy, it can cross the placenta and enter the foetal blood circulation. Importantly, the foetal brain is made up of 60% fat, which stores high levels of THC. The brain is also densely populated with endocannabinoid receptors that carry out THC’s psychoactive effects.

Some known effects of THC on the embryo development include:

  • Reduce levels of folic acid uptake, which could increase risks of neural tube defects and low birth weight
  • Interfere with critical pathways for cellular growth and formation of new blood vessels
  • Affect the transition from stem cells to brain cells, which could damage learning and memory functions

More recently, a study published on the Medical Journal of Australia evaluated 5610 pregnant women, including 314 women who used cannabis before or during their first trimester.

The researchers found that compared to babies of mothers who didn’t use cannabis, newborns from mothers who continued to use cannabis are smaller. They were also born at an earlier age on average. Following birth, these babies also had more breathing problems. They were twice as likely to be admitted to a specialist neonatal unit as compared to babies of mothers who didn’t use cannabis.

Previous studies from the United States and Canada have found similar trends, where cannabis use during pregnancy is associated with reduced birthweight, birth length, head circumference, pre-term delivery or other developmental complications.

In addition to affecting embryo development, evidence suggests that cannabis also affects implantation, which is when a fertilised egg attaches to the uterine wall to result in a pregnancy.

Implantation is less likely to be successful because:

  • Fallopian motility can be impaired, thereby preventing the fertilised egg from reaching the uterus
  • A higher likelihood of ectopic pregnancy outside the uterus
  • The cannabinoids from cannabis may bind to receptors in the uterus and make it toxic for an incoming embryo

Verdict: Avoid

What about health benefits of cannabis during pregnancy? At this point, we don’t have any compelling evidence to suggest that it is an effective treatment for any disorder. The conclusion is straightforward: Given the adverse outcomes associated with cannabis use during pregnancy, the risks far outweigh the benefits (if any at all).

If you are planning a pregnancy

The advice is to cut back or stop cannabis use as early as possible to prevent some of the harms. You may want to consider seeing a counsellor for help, who can assist you in:

  • Identify personal issues and how to overcome them
  • Learn healthy ways to manage stress and problems
  • Recognise triggers that may increase your cannabis use
  • Develop strategies to stop using cannabis and other addictive substances
  • Be a better parent

For more personalised help on your pregnancy journey, you can consult Melbourne-based obstetrician and fertility specialist, Dr Alex Polyakov.