Avoid marijuana to cut pre-term birth risk

Having marijuana through to 20 weeks' gestation can trigger a five-fold increase in the risk of pre-term birth, Australian researchers have warned.

"The results suggest that more than six percent of pre-term births could have been prevented if women did not use marijuana during pregnancy, irrespective of other risk factors," said lead study author Claire Roberts from Adelaide's Robinson Research Institute.

The team analysed more than 5,500 pregnant women from Australia, New Zealand, Ireland and Britain. 

They also considered a range of risk factors -- such as cigarette smoking, age, obesity and socio-economic status -- and their links to serious pregnancy complications.

The results found that the Australian participating centre had the highest rate of women using marijuana before or during pregnancy 12 percent, followed by New Zealand five percent, Ireland four percent and Britain four percent.

“Continued marijuana use in pregnancy has been independently linked to pre-term birth. Based on our findings, we consider marijuana to be a major public health concern for pregnant women and their babies," Roberts added in the paper published in the journal Reproductive Toxicology.

The proportion of very early pre-term birth was also higher, with 36 percent of marijuana users having delivered at less than 28 weeks' gestation and 64 percent at less than 32 weeks,

The study was unable to determine whether there is a 'safe' time prior to 20 weeks' gestation to give up marijuana. 

"But we recommend total abstinence from marijuana during pregnancy," Roberts stated.