Mothers who engage in recreational drug use during pregnancy may be at higher risk of having a baby with a brain defect at birth, researchers find.
The research team, led by Dr. Anna David of the Institute of Women's Health at University College London, publish their findings in the journal PLOS ONE.
Past studies have associated recreational drug use in pregnancy with offspring birth defects, but Dr. David says many of these studies may be inaccurate as they have relied on self-reporting.
For this study, the researchers enrolled 517 mothers and tested samples of hair to determine their drug use around the time of conception and during pregnancy.
The team explains that when a person takes drugs, traces from the drugs accumulate in their hair as it grows. Since hair grows around 1 cm each month, the team took a 9-cm sample of hair from each woman to estimate their drug use for the previous 9 months.
Of the participants, 213 had a baby with a birth defect with possible links to recreational drug use, 143 had a baby with a birth defect not previously associated with recreational drug use, while 161 had a baby with no birth defect.
Drug use in pregnancy linked to brain underdevelopment, brain cysts in offspring
The team found that 77 (14.9%) of the women tested positive for the use of at least one recreational drug; 68 of the women had taken cannabis, 18 took cocaine, one took ketamine and one took MDMA (ecstasy).
The highest levels of recreational drug use were found around the time of conception but reduced by the first or second trimester of pregnancy. Approximately 50% of women who smoked cannabis, however, carried on using the drug into the second trimester.
The researchers found that 35% of the women whose baby was born with a brain birth defect - including brain cysts and brain underdevelopment - had engaged in recreational drug use at conception or during pregnancy, compared with 13% of women who had a baby without a birth defect.
Such brain defects at birth, the researchers say, are a major concern; they can have severe outcomes and lead to lifelong disorders, such as cerebral palsy.
Commenting on the results, Dr. David says:
"Our findings suggest a link between brain birth defects and recreational drug use in expectant mothers.
We were unable to identify significant links between specific drugs and brain birth defects. Therefore, I would discourage women trying to get pregnant and those in early pregnancy from taking any recreational drugs, including cannabis."
She adds, however, that only 20 of the mothers in the study had a baby with a brain defect at birth, therefore a larger study is warranted to confirm the findings - something she hopes will happen now that this study has indicated a link.
"The risks of alcohol and tobacco in pregnancy are relatively well-researched," she adds, "and we hope that research into drug use will catch up now that we have demonstrated its relevance to babies' health and development."
Last year, Medical News Today reported on a study suggesting that exercise during pregnancy can benefit offspring brain development.