Use of cannabis during pregnancy is linked to low birthweight and the subsequent need for intensive care, according to US researchers.
They cautioned that, as cannabis became more socially acceptable, it was important that prospective mothers and clinicians were fully informed on the potential harms of using the drug during pregnancy.
“There does appear to be negative consequences associated with in utero exposure to cannabis”
They noted that, while previous research had focused on the drug and potential links to respiratory and mental illness, less was known about its possible effects on foetal growth and development.
The researchers trawled seven research databases for studies published up to 2014, looking at the effects of cannabis use during pregnancy on mother and baby up to six weeks after the birth.
Outcomes, such as anaemia in the mother, birthweight, baby’s length, need for neonatal intensive care, head circumference and early birth were all included in the review of 24 studies.
Analysis of the data showed that mothers-to-be who used cannabis were 36% more likely to have anaemia than women who did not use the drug.
Infants exposed to cannabis in the womb were 77% more likely to be underweight at birth and twice as likely to require intensive care as those whose who had not used cannabis during pregnancy.
The researchers acknowledged they were unable to extract data on whether any of the study participants used other illicit drugs or how much alcohol they drank – factors known to be associated with a higher risk of low birthweight and premature birth.
However, they stated: “There does appear to be negative consequences associated with in utero exposure to cannabis, including a decrease in birthweight and a need for placement in [intensive care].”
As medical and social use of the drug “is rapidly becoming more acceptable”, understanding its effects on maternal and foetal health “should become a global priority,” they said in the journal BMJ Open.
Women and their clinicians could do with more information on the possible harms of using the drug during pregnancy, they added.