Lead author Dr. Beatriz Tapia, a lecturer at the University of Texas Health Science Center -- Regional Academic Health Center campus in Harlingen, Texas, located 10 miles from the Mexican border -- said all the women were in the third trimester of pregnancy, when the fetal brain undergoes a growth spurt.
Studies have reported pesticide exposure might adversely affect mental and motor development during infancy and childhood. Pregnant women and infants often spend 90 percent of their day indoors, Tapia said.
Two-thirds of the families surveyed in the study said they used pest control methods to kill cockroaches, rodents and other pests. Pregnant women and infants often spend 90 percent of their day indoors.
The research team sampled air in 25 households, finding at least five pesticides in 60 percent of the dwellings. Nine other pesticides were identified in less than one-third of the homes.
The study, published in the summer issue of the Texas Public Health Journal, found 92 percent of the air samples contained o-phenylphenol, which is used as a fungicide, germicide and household disinfectant, while 80 percent included chlorpyrifos, employed in agriculture to kill mosquitoes and other pests.
In addition, propoxur, present in granular baits, pet collars and other products, showed up in 76 percent of samples, along with the insecticide diazinon in 72 percent. The herbicide trifluralin turned up in 60 percent of samples, the study said.
Notable deaths of 2014 [PHOTOS]