The mosquito coast

Of all the animals languishing below humans on the food chain, the mosquito must be one of the most worthy pretenders to the throne. Like rats in the times of the great plagues, no other animal seems to have quite the knack of killing off large swathes of human population (the birds tried for a while with bird flu but didn’t quite cut it). 219 million people contract malaria across the globe every year which combined with the effects of West Nile virus, yellow fever and dengue fever make the humble mosquito quite the foe in the race to survive. And as with everything else, with your immunity suppressed to allow an alien to inhabit your womb, the effects of getting any of these diseases on you and the baby are so much worse than they would have been pre-pregnancy.

Malaria medication is tricky when pregnant or trying to conceive, with the more powerful anti-malarials off the table entirely. So that leaves prevention as the cure. There are various prevention options open to you – wearing clothing that covers your skin up; using insect repelling citronella, coils or plug-ins; not going to places where mosquitos harbour noxious diseases is another option; or the standard approach (at least when not pregnant) – bug spray.

Bug spray or insect repellent in its most effective form will contain DEET or Diethyl Toluamide to its friends. So as with virtually every action I take nowadays, the question is whether it’s safe for the alien or is it like tiramisu (a new item on the “not allowed” list) a virulent harbinger of destruction?


It seems the jury weighs on the side of DEET on this one. The clear advice is that malaria is definitely worse than anything DEET can do, so if you have to travel to a place where you are at risk of malaria then reach for the bug spray. Where the risk is virtually nonexistent like the UK, then you might take the cautious route whilst pregnant. But what about where there is a low risk of a serious illness, such as Guadeloupe where a few years ago there was a dengue fever outbreak (much like the one in Madeira last year), but which seems to be harbouring common-or-garden mozzies nowadays rather than the biological-warfare types?

The majority of the evidence seems to suggest no adverse effects from using DEET during pregnancy. The one study which goes against this suggested a link between use of DEET in the first trimester and hypospadias in boys (hypospadias being a birth defect where there is a problem with the foreskin of the penis), but critiques of this study have questioned whether this finding was purely related to use of the DEET. The HPA and NHS (via babycentre) declare that products using up to 50% DEET are safe for use in pregnancy – although OTIS (the Organization of Teratology Information Specialists who seem to be the experts on the subject in the US) seem to err on the side of caution and suggest that using the 20% variety it better since the percentage apparently only affects the duration that the protection will provide and at 4 hours’ protection 20% will often be sufficient.

Yet, I need to be mindful that 10% of DEET applied can enter the bloodstream and hence cross the placenta. Indeed, on a median dose one study found it rocking up in 8% of cord blood samples, and although that study found no adverse effects on “survival, growth, or development at birth, or at one year”, I’m still mindful that it’s a toxin.

So much like anything it comes to weighing up the risks and making a choice. I think the risk of getting dengue fever in Guadeloupe is low, and the literature reviews suggest that except in extreme cases the impact may be low for both mother and baby (a link between dengue fever and prematurity is found in some studies but not others).

Either way, I’m not sure I want to find out. So I am taking a combined approach – wearing long dresses and long sleeves in the evenings and so only having to douse those areas which are exposed to insect repellent. Sadly in April there aren’t many options in Europe with guaranteed sun, and so on balance I think the increased exercise (swimming in the sea!) and vitamin D from the sun (the effects of deficiency in which are worthy of a post in its own right) outweigh the risks from dengue or DEET. Fingers crossed I’m right…

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