Between four and five percent of pregnant women report some level of cannabis use. This level decreases markedly throughout pregnancy. Many women who report using cannabis during pregnancy do so to address symptoms of nausea/morning sickness.
In utero cannabis exposure is not independently associated with low birthweight, pre-term birth, or other adverse neonatal outcomes
"A study was carried out in 4465 infants whose mothers delivered during 2017 and 2018. Self-reported maternal smoking, e-cigarette and cannabis use at booking were recorded. Outcome measures were birthweight and head circumference z-scores and admission to the neonatal intensive care unit (NICU). ... Cannabis use alone was not associated with a significant reduction in birthweight or head circumference z-score, but the combination of cannabis and cigarette smoking resulted in a significant decrease in both z-scores compared to cigarette smoking alone."
"[O]verall prevalence of marijuana use during pregnancy was low. ... [M]arijuana use during pregnancy was not independently associated with infant birth weight or gestational age, after controlling for confounding. ... Further, we did not observe significant effects of marijuana use during pregnancy and preterm birth or healthcare utilization."
"[M]aternal marijuana use during pregnancy is not an independent risk factor for low birth weight or preterm delivery after adjusting for factors such as tobacco use. There also does not appear to be an increased risk for other adverse neonatal outcomes such as SGA (small for gestational age) and placental abruption once we account for other influencing factors. … [T]he results of this systematic review and meta-analysis suggest that the increased risk for adverse neonatal outcomes reported in women using marijuana in pregnancy is likely the result of coexisting use of tobacco and other cofounding factors and not attributable to marijuana use itself."
"After adjustment for confounding, cannabis use was not associated with mean birth weight or gestational age or with low birth weight or preterm delivery. … Reported cannabis use does not seem to be associated with low birth weight or preterm birth."
"The infants were not significantly different in the groups (as distinguished between marijuana using mothers and mothers who did not use cannabis) according to physical exam data including birth weight and length and gestational age."
In utero cannabis exposure is not independently associated with significant, consistent adverse effects on childhood development
RESOURCES: Breathe, Push, Puff? Pot Use and Pregnancy: A Review of the Literature, NORML, 2009 | Women and Cannabis: Medicine, Science, and Sociology, Haworth Press, 2002
"The evidence base for maternal-infant health outcomes of cannabis use in pregnancy is more robust than for many other substances. … Although there is a theoretical potential for cannabis to interfere with neurodevelopment, human data drawn from four prospective cohorts have not identified any long-term or long lasting meaningful differences between children exposed in utero to cannabis and those not."
"Neither maternal nor paternal cannabis use was associated with educational attainment (in their children) in observational analyses, but few mothers in our sample used cannabis regularly in pregnancy."
"This research provides data on the development of 59 Jamaican children, from birth to age 5 years, whose mothers used marijuana during pregnancy. … The results show no significant differences in developmental testing outcomes between children of marijuana-using and non-using mothers except at 30 days of age when the babies of users had more favourable scores on two clusters of the Brazelton Scales: autonomic stability and reflexes. The developmental scores at ages 4 and 5 years were significantly correlated to certain aspects of the home environment and to regularity of basic school (preschool) attendance."