How Bad Is Marijuana for Pregnancy?

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The Pulse recently reported on a study in Journal of the American Medical Society (JAMA)  which found that the number of women who reported marijuana use in pregnancy had doubled between 2002 and 2017.

This is not too surprising since marijuana for recreational or medical use is now legal in most states. For many years, the American College of Obstetricians and Gynecologists (ACOG) has been cautioning pregnant women about possible risks for them and their developing babies from marijuana. However, there was always the added statement that the warnings were based on limited research. Thus, the use of the term “possible.”

For many pregnant women, the move towards legalization, and the limited research may have taken the edge off the ACOG warnings. Now, a new study from Canada adds some more research, and it supports what ACOG has been saying.

This research is also reported in JAMA. Canadian researchers compared 5,639 pregnant women who admitted marijuana use to a larger group of women who did not use marijuana between 2012 and 2017. There were lots of significant and worrisome risks for the users. Compared to the non-users, they had these relative risks:

  • A 41% higher risk of preterm birth (before 37 weeks)
  • A 53% higher risk of a small for gestational age baby
  • A 72% higher risk for placental abruption
  • A 40% higher risk for a baby needing transfer to intensive care
  • A 28% higher risk of a baby with a 5-minute Apgar score less than 4

Preterm birth was the risk the researchers were most interested in (the primary study outcome). Preterm birth can increase a baby’s risk for developmental delays and a lifetime of problems. Placental abruption is a rare but potentially dangerous (possible fatal) complication for both mother and baby, caused by detachment of the placenta from inside the womb before delivery.

Taken together, the two JAMA studies point to a developing problem. There is more evidence that use of marijuana is dangerous during pregnancy, combined with evidence that more women are taking the risk.

Obviously, this is a risk you should avoid. Some key takeaways from ACOG’s most recent marijuana and pregnancy guidelines:

  • Marijuana may affect your baby’s brain development.
  • You may be putting yourself at higher risk for lung damage, falls, or injury.
  • You may be putting you and your baby at risk for several dangerous birth and near-birth complications.
  • There is no evidence that medical marijuana helps morning sickness or has any other use in pregnancy.

Bottom line, the best advice is to avoid marijuana if you are trying to become pregnant or may become pregnant. Stop using marijuana if you do become pregnant. If you are struggling to stop using, ask for help. Legalizing marijuana or calling it medical does not make it safe, especially during pregnancy.

Christopher Iliades
Dr. Chris Iliades is a medical doctor with 20 years of experience in clinical medicine and clinical research. Chris has been a full time medical writer and journalist since 2004. His byline appears in over 1,000 articles online including EverydayHealth, The Clinical Advisor, and Healthgrades. He has also written for print media including Cruising World Magazine, MD News, and The Johns Hopkins Children's Center Magazine. Chris lives with his wife and close to his three children and four grandchildren in the Boston area.

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