Maternal lead exposure and the secondary sex ratio.

BACKGROUND A reduction in the secondary sex ratio may be associated with exposure to environmental toxicants. Little data exists relating this outcome to lead exposure, a well-known reproductive toxicant. METHODS We studied 1980 women having singleton births from 1994 to 1995 and from 1997 to 2001 who participated in a cohort study of lead exposure and infant outcomes in Mexico City. Levels of lead were measured in maternal and cord blood using graphite furnace atomic absorption spectroscopy, and levels of lead in maternal patella and tibia bone (a reflection of cumulative exposure) were measured using noninvasive K-X-ray fluorescence measurements. Using logistic regression models, we evaluated the relations of these measures to secondary sex ratio in the offspring, adjusting for maternal age, parity and year of infants' birth. RESULTS We found no consistent association between any of the lead measures and secondary sex ratio. Results were unchanged when we adjusted for infants' year of birth, maternal age and parity. CONCLUSIONS Despite a large sample size and the use of sensitive biomarkers, we did not find evidence that maternal and fetal lead exposure is associated with a lower secondary sex ratio among newborns.