Tommy's PregnancyHub

New study shows cannabis can increase risk of premature birth

A recent study suggests the risk of premature birth doubles if cannabis is used during pregnancy.

Results from a recent study in Canada have shown that using cannabis during pregnancy can double the risk of babies being born prematurely. It has also found a link between using cannabis and a greater risk of developing birth complications such as placental abruption. This is where the placenta comes away from the wall of the womb, which can cause serious problems. 

Key findings from the study:

  • 12% of women who took the drug gave birth prematurely (before 37 weeks).
  • Only 6.1% of women who said they did not take the drug gave birth prematurely.
  • The risk of placental abruption was 66% higher in women who said they took cannabis and there was also a marked increase in the need for the baby to have intensive care after birth. 

Medicinal cannabis has been legal in the UK since 2018. It is illegal to use medicinal cannabis without it being prescribed by a doctor. We still do not know all the benefits and risks of cannabis-based medicines, and guidelines are likely to develop as more research is done. This particular study has not looked at how cannabis is taken by pregnant women and whether this affects the results.   

The results of this study are particularly important, because another study in the US has found an increase in women using forms of cannabis to treat morning sickness. Women are currently being advised not to use cannabis during pregnancy and to find other alternatives.

About premature birth

A premature birth happens when a baby is born before 37 weeks. There are different levels of prematurity:

  • extremely preterm (less than 28 weeks)
  • very preterm (28 to 32 weeks)
  • moderate to late preterm (32 to 37 weeks).

In some cases, it is possible to know the cause of preterm birth. For example, women who are having twins are at a higher risk and some women may have a planned preterm birth because of pregnancy complications. But often, the causes are unknown or unclear.

Premature birth can cause problems for the baby, because they have not finished fully developing. But it is important to remember that if your baby is born prematurely, hospitals will support them with neonatal care until they are ready for life outside the womb.

If you are worried, we have lots more information about premature birth.

How drugs can affect pregnancy

It can be hard to tell health professionals if you have taken, or are continuing to take, drugs during pregnancy. But it is important you get the support you need. Talk to your midwife - there's no need to worry about being judged or feeling guilty. They are there to help and support you.

Our midwife Kate says:

"It is important that GPs and health professionals offer confidential and supportive advice to women who need it. This will help women reduce and stop taking any harmful drugs before, or at least as soon as they know they are pregnant. It is vital, that family members and friends are also supportive. An excellent advice line is available through FRANK, who offer friendly and confidential drug advice by phone or email."

More information

Find out how to Talk to FRANK.

We also have more information on how taking drugs can affect pregnancy.