Reproductive effects of Cannabis

High doses of cannabis cause growth retardation and malformations in animals, but epidemiological studies have given scarce evidence for an increased risk of birth defects in women who use cannabis during pregnancy.

Interpretation of the few associations that have been reported is difficult because cannabis users are also more likely to use tobacco, alcohol, and other illicit drugs during pregnancy, and less likely to seek antenatal care and have poorer nutrition than women who do not use cannabis.

Source: Review | www.thelancet.com | Vol 374 October 17, 2009
Adverse health effects of non-medical cannabis Use by Wayne Hall, Louisa Degenhardt

For over two decades, cannabis, commonly known as marijuana, has been the most widely used illicit drug by young people in high-income countries, and has recently become popular on a global scale. Epidemiological research during the past 10 years suggests that regular use of cannabis during adolescence and into adulthood can have adverse effects. Epidemiological, clinical, and laboratory studies have established an association between cannabis use and adverse outcomes. We focus on adverse health effects of greatest potential public health interest—that is, those that are most likely to occur and to affect a large number of cannabis users. The most probable adverse effects include a dependence syndrome, increased risk of motor vehicle crashes, impaired respiratory function, cardiovascular disease, and adverse effects of regular use on adolescent psychosocial development and mental health.

No increased risk of birth defects could be seen in a large group of women who use cannabis. Cannabis use in pregnancy has been most consistently associated with reduced birthweight in large epidemiological studies.

A meta-analysis showed that regular cannabis smoking during pregnancy decreased birthweight, probably through the effects of carbon monoxide on the developing fetus.Mild developmental abnormalities have been reported in children born to women who used cannabis during pregnancy.

These include developmental delay in the visual system shortly after birth, and increased tremor and startle; other studies have given mixed results. Day and colleagues followed up children born to 655 women and found poorer performances on memory and verbal skills. By 10 years of age, children born to cannabis users showed increased delinquency and behavioral problems.

The causal interpretation of any such effects is weakened by the inability of these studies to control for the confounding effects of other drug use during pregnancy, poor parenting, and genetic factors.