Mosquito spraying in your area while pregnant

What does the evidence say about neighborhood mosquito spraying during pregnancy?

1. Bystander dermal exposure to permethrin from truck-mounted ultra-low-volume mosquito spraying was estimated at about 0.0004 percent of the reference dose, which researchers called negligible and well below regulatory levels of concern. 1
2. It's unlikely that having your home, workplace, or neighborhood sprayed by a professional exterminator or municipal program will result in a high enough pesticide exposure to increase risks to a pregnancy, though avoiding personally mixing or applying pesticides yourself is still recommended. 2
3. Human studies following repeated spraying of malathion, and a study of 113 women who used a pyrethroid cream for head lice during pregnancy, did not find a consistent increase in birth defects above the background rate. 2
4. In New York City, pyrethroid spraying for West Nile virus control was not followed by a population-level increase in emergency department visits for asthma, with 510 visits in the 3 days before spraying versus 501 in the 3 days after, across 62,827 total asthma visits studied. 3
5. Animal studies suggest very high prenatal pyrethroid doses, well above typical human exposure levels, may affect learning and behavior, but obstetric organizations still recommend pyrethroid-based products for mosquito protection when weighed against the well-documented risks of mosquito-borne illness like Zika to a developing fetus. 4

Is neighborhood mosquito spraying safe in each trimester?

• First trimester. No trimester-specific spraying data exists, but the reassuring bystander exposure studies, deposition far below regulatory limits, apply throughout pregnancy, including the first trimester when organ development is most sensitive.
• Second trimester. The same low-exposure findings hold in the second trimester. If you want extra reassurance, closing windows and staying inside during the actual truck or plane pass keeps outdoor drift exposure even lower.
• Third trimester. By the third trimester, the balance of evidence, negligible bystander exposure, no asthma emergency-visit signal, no consistent birth defect increase from pesticide spraying studies, still favors normal outdoor activity, with the same simple precaution of avoiding being directly outside during a spray pass.