Lead exposure during pregnancy may affect the baby's hearing in the first days of life
Even at levels considered low, lead exposure during pregnancy may be associated with subtle changes in newborn hearing function. In an article published in the journal Environmental Research: Health, researchers from Projeto Infância e Poluentes Ambientais, PIPA/UFRJ, investigated the relationship between lead levels in umbilical cord blood and the results of newborn hearing screening performed in the first days after birth.
The study, entitled "Prenatal lead exposure and neonatal hearing screening outcomes in newborns from the PIPA cohort project, Rio de Janeiro", evaluated 434 newborns participating in the PIPA birth cohort.
The researchers measured lead concentrations in umbilical cord blood samples and analyzed the response of the cochlear hair cells through transient evoked otoacoustic emissions, a test used in newborn hearing screening.
The results showed that higher lead concentrations were associated with reduced auditory responses at high frequencies, especially at 4 kHz in the right ear. The association was more evident among girls, who showed significantly smaller responses when exposed to higher levels of the metal during pregnancy, even after adjustment for factors such as maternal education, smoking, and drug use.
One finding that caught the researchers' attention was that the effects were observed at lead concentrations below the reference value adopted by the Centers for Disease Control and Prevention (CDC) of the United States. In addition, lead was detected in virtually all umbilical cord blood samples analyzed, evidencing the widespread exposure of the population to the metal.
Although the identified changes do not represent clinical hearing loss, they may indicate early impairment of cochlear function — a structure essential for hearing and for language development in the first years of life. The authors emphasize that the results reinforce the need for policies to prevent exposure to heavy metals during pregnancy and to integrate environmental surveillance into maternal and child health actions.
