Pre-conception exposure to low doses of malathion during the juvenile and pubertal periods impairs placentation and offspring fetal development in female Wistar rats.

Malathion is an insecticide widely used in agriculture and, in Brazil, was heavily applied in the 2010s to control Aedes mosquitoes. Its use exposes the general population, including children and adolescents, to this pesticide. As puberty reflects the maturing of the reproductive system, this study investigated whether preconception exposure to low doses of malathion during juvenile and pubertal stages affects fertility and pregnancy outcomes in Wistar rats. Female rats received daily gavage doses of 10 or 50 mg/kg from postnatal day (PND) 22 to 60. Puberty onset was monitored starting on PND 27. Following exposure, females were mated at the first proestrus and euthanized on gestational day (GD) 18. Malathion advanced puberty onset (M50) but did not impair fertility or serum hormonal levels. Females exposed to the higher dose showed increased urea levels. Additionally, placental integrity was compromised, with reduced placental glycogen (M10) and increased oxidative stress and reduced offspring CRL. These findings indicate that preconception exposure to low doses of malathion negatively impacted placentation and offspring's intrauterine development at GD 18.