The study, led by epidemiologists at the Stanford University School of Medicine, analyzed thousands of birth records and commercial pesticide application records for eight counties in California's heavily agricultural Central Valley.
They aimed to determine if kids were at higher risk of hypospadias if their moms had lived in close proximity to where pesticides were used while pregnant.
Hypospadias is a genital malformation in which the urethral opening is on the underside of the penis rather than on the tip.
In the most detailed study of the largest data sets done to date, 292 individual chemicals and 57 groups of structurally similar chemicals were analyzed. Of those, the study identified 15 that had possible associations with hypospadias.
Lead authors Suzan Carmichael, PhD, associate professor of pediatrics, said that they didn't see many chemicals that suggested an increased risk, and of those that did, most of them were infrequently used.
The study population included all male infants born from 1991 to 2004 to mothers residing in any of the eight counties at the time of birth. The study sample comprised 690 cases of hypospadias, as well as 2,195 controls randomly selected for comparison.
The researchers considered pesticides used within 500 meters of the mother's residence during weeks one to 14 of each pregnancy. Urethral development typically occurs between weeks four and 14.
The study has been published in journal Pediatrics.