Summary
Threadworm/pinworm infestation (enterobiasis), unless overwhelming, is not usually considered a serious threat to health, therefore infestation in pregnancy should, if possible, be eradicated by rigorous attention to hygiene for at least six weeks. If drug treatment is considered necessary, it should ideally be delayed until after the first trimester.
The data on first trimester mebendazole use do not suggest an increased risk of congenital malformations overall, or of any specific malformations, although the data consist of only ~1,200 first trimester exposures so are insufficient to exclude a risk. No increase in the rate of spontaneous abortion, perinatal death, small for gestational age, or differences in gestational age at delivery were found between exposed and unexposed infants. No studies were identified which investigated neurodevelopment, neonatal complications or carcinogenicity in the offspring.
In the treatment of threadworm/pinworm in pregnancy, mebendazole could be considered after first attempting rigorous hygiene measures. When used in the treatment for hookworm, and if required during the first trimester, the benefit of treatment with mebendazole may outweigh any risk.
Exposure to mebendazole at any stage in 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.
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