Continued Use of Marijuana in Pregnancy is Risk for Both Mother and Baby Interview with:

Professor Claire Roberts PhD Professor Claire Roberts Robinson Research Institute Adelaide University

Prof. Claire Roberts

Professor Claire Roberts PhD

Robinson Research Institute
Adelaide University What is the background for this study? What are the main findings?

Dr. Roberts: Our research aimed to identify novel risk factors for the four main complications of pregnancy;

  • preeclampsia where the mother gets high blood pressure and her kidneys don’t work properly,
  • preterm birth which is delivery before 37 weeks of gestation,
  • small for gestational age and
  • gestational diabetes.

    We have studied over 5500 pregnant women in 6 centres in 4 countries, Australia, New Zealand, the UK and Ireland. We have identified a number of factors that contribute to these major pregnancy complications. However, in this paper we have focused on well known risk factors for pregnancy complications including maternal cigarette smoking, BMI and socioeconomic status. To these we added maternal use of marijuana before pregnancy, in first trimester, at 15 weeks and at 20 weeks gestation. After adjusting the data for the other factors, we found that continued maternal marijuana use at 20 weeks gestation is strongly associated with spontaneous pre-term birth independent of maternal cigarette smoking. Women who continued to use marijuana at 20 weeks’ gestation were over 5 times more likely to deliver preterm than women who did not use marijuana. Previous studies have shown conflicting evidence but none have accounted for maternal cigarette smoking.

Importantly, not only did continued use of marijuana increase risk for preterm birth but it also made these births 5 weeks earlier on average with a greater number of women delivering very preterm. That is much more dangerous for the baby who inevitably would require admission to a neonatal intensive care unit (NICU). Earlier delivery would be expected to increase the baby’s risk for dying and having long term disabilities. What should readers take away from your report?

Dr. Roberts: Across all the recruiting centres 5.6% of women were using marijuana regularly before or during pregnancy and 1% continued to use it at 20 weeks’ gestation. This is a lot more than we anticipated and more than most people would expect. Continued use of marijuana in pregnancy is risky for both mother and baby. If women smoke marijuana before pregnancy it is best to stop if planning pregnancy or as early in pregnancy as possible. What recommendations do you have for future research as a result of this study?

Dr. Roberts: Future research should determine what marijuana use does to the placenta and by what mechanism does it act to precipitate preterm birth. Is there anything else you would like to add?

Dr. Roberts: Women with low socioeconomic status (SES) were more likely to be using marijuana before and during pregnancy than women of high SES. Women with low SES are less equipped to provide for a child who has significant disability than more affluent women.

Anecdotally, some women are using marijuana to alleviate nausea associated with morning sickness in pregnancy. There is no evidence that it actually helps this. We advise women to abstain from using marijuana during pregnancy. Thank you for your contribution to the community.


Shalem Y. Leemaqz, Gustaaf A. Dekker, Lesley M. McCowan, Louise C. Kenny, Jenny E. Myers, Nigel A.B. Simpson, Lucilla Poston, Claire T. Roberts.Maternal marijuana use has independent effects on risk for spontaneous preterm birth but not other common late pregnancy complications. Reproductive Toxicology, 2016; 62: 77 DOI: 1016/j.reprotox.2016.04.021

Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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Last Updated on May 18, 2016 by Marie Benz MD FAAD