A paper published in the journal PLOS One has analysed the use of recreational drugs in women with normal pregnancies and those with foetal abnormalities. In a small sample size, they reported an increased incidence of foetuses with gastroschisis born to younger mothers, and an increase in abnormalities of the central nervous system in foetuses born to mothers who used recreational drugs before conception.
Prof David Nutt, The Edmond J Safra Chair and Head of the Centre for Neuropsychopharmacology, Imperial College London, said:
“The only drugs they have in the sample in any numbers are cannabis and cocaine, so I’d question the use of the catch-all term ‘recreational drug use’, which is not really a scientific concept. In fact, given the numbers involved, the only likely significant effect is from cannabis so I’d suggest they should do the analysis for this drug alone.”
Prof Andrew Whitelaw, Professor of Neonatal Medicine, University of Bristol, said:
“This paper did not find a link between maternal recreational drug use and gastrochisis but provides evidence of other dangers to the fetus. The authors should be commended on using hair analysis, the most reliable method of identifying recreational drug use in pregnancy, as studies based on questionnaire or analysis of urine are likely to seriously underestimate.
“Such research is very difficult because large numbers are needed for confident conclusions. Despite recruiting for 4 years in 4 large fetal medicine departments, they only identified 18 women taking cocaine and one taking ecstasy. This is reassuring in one sense but such small numbers mean it is virtually impossible to examine the effect of such drugs in pregnancy.
“The conclusions mainly concern cannabis, which was taken by 68 women. The conclusion that recreational drugs are associated with an increased risk of various brain abnormalities is based on 7 out of 20 abnormal fetal brain pregnancies being positive for a recreational drug versus 13 out of the 20 being negative so needs to be retested in a much larger population.
“This study dealt only with structure and did not investigate whether recreational drugs have an adverse effect on the function of the developing brain. As the whole point of taking these drugs is to affect brain function, this is a more likely and a more worrying possibility.”
Prof Nigel Brown, Professor of Developmental Biology and Head of Division of Biomedical Sciences at St George’s, University of London, said:
“The authors of this study advise that women trying to get pregnant, and those in early pregnancy, should not take any recreational drugs including cannabis. This is appropriate and prudent advice and in line with current practice. No further conclusions can be drawn from this work, although the approach of using hair analysis as an indicator of drug use is useful for some types of study.
“The study has many limitations, including: Many different types of recreational drugs were grouped together, so no conclusions can be drawn on the hazard of any individual drugs; There was only one apparently significant association between recreational drug use and a type birth defect, that of non-neural tube defect (NTD) central nervous system (CNS) anomalies, which is a mixed group of unrelated brain defects. However, there were only 20 such defects in the study (13 from mothers who did not take recreational drugs) which is not sufficient to be able to draw any definitive conclusions.
How much of an impact did the drugs have?
“We already knew that cannabis and cocaine were harmful for foetuses and it is not possible to tell from this study how much of an impact the drugs had.”
Didn’t we already know that cannabis and cocaine etc were harmful for foetuses?
Is it surprising that 15% of pregnant Mum’s took recreational drugs? How much of that was a result of not knowing they were pregnant?
“This study was not designed to find out what proportion of all mums take recreational drugs. Overall, the results are not shown in a way that distinguishes between early stages, when pregnancy might not be known, and later stages.”
Do we know similar numbers for alcohol and cigarettes – how do the relative harms for the child compare?
“The study does not allow any conclusions to be drawn about relative harm.”
Is there a particular time during pregnancy when drugs are most harmful?
“The study does not address this question.”
Does this evidence change any existing guidelines/practices?
“No, overall this study presents no significant new knowledge, except perhaps the conclusion that recreational drug use is not associated with gastroschisis.”
‘A Case-Control Study of Maternal Periconceptual and Pregnancy Recreational Drug Use and Fetal Malformation Using Hair Analysis’ by Anna David et al. published in PLOS One on Friday 31st October.