Insect repellents are agents applied to the skin, clothing and/or bed nets to deter biting insects such as mosquitos and ticks. They are important in the prevention of mosquito-borne infections such as malaria, Zika virus, dengue fever and yellow fever, and tick-borne infections including Lyme disease and tick-borne encephalitis.
Pregnant women should be advised against travel to areas where there is a risk of mosquito-borne infection, and should be aware that rates of Lyme disease transmission vary locally and globally. Ticks are most commonly found in forest fringes, forest glades, riverside meadows and marshland, and forest plantations with brushwood and shrubbery.
When exposure to environments where insect bites may lead to serious illness is unavoidable, non-pharmacological preventative measures are important. These include staying indoors at the times of day when mosquitos are most active, using bed nets impregnated with insecticide to avoid mosquito bites, and minimising skin exposure when outdoors by wearing long sleeves and trousers (including tucking trousers into socks where there is a risk of mosquito/tick exposure). Insect repellent should be applied to clothing and exposed skin according to the manufacturer’s instructions, and washed off once returning indoors. Ticks should be removed from the skin intact as soon as possible to reduce the risk of transmission of tick-borne disease.
The use of diethyl-m-toluamide (DEET) 20-50% is recommended first-line for all pregnant women, at any stage of pregnancy, travelling to a malarial area. The benefits of using DEET in these circumstances are likely to outweigh any risk of harm. There are, however, limited data on the use of DEET in human pregnancy, especially in the first trimester. One case-control study has reported an association between use of insect repellent (not specifically DEET) in pregnancy and hypospadias in male infants, however more data are required to accurately assess the risks. A single study found no adverse effects on fetal growth and postnatal development in the offspring of women who used DEET 20% in the second and third trimesters of pregnancy.
P menthane-3,8-diol (PMD) and picaridin (icaridin) ≥20% are possible alternatives to DEET containing products, although PMD should not be used where there is a risk of malaria as it may not afford an appropriate level of protection. There are no data relating to exposure to these agents in human pregnancy, however animal studies have not demonstrated any features of maternal or developmental toxicity.
Exposure to insect repellents, according to the manufacturer’s instructions, at any stage of pregnancy would not usually be regarded as medical grounds for termination of pregnancy or any additional fetal monitoring. However, other risk factors may be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.
Note: Where travel to a malarial area during pregnancy is unavoidable, additional prophylaxis will be necessary. Please consult the Malaria Prophylaxis monograph or contact UKTIS on 0344 892 0909 for more information.
This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to NHS health care professionals who are logged in.
If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.
If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.