Reduced intellectual development in children with prenatal lead exposure.
OBJECTIVE
Low-level postnatal lead exposure is associated with poor intellectual development in children, although effects of prenatal exposure are less well studied. We hypothesized that prenatal lead exposure would have a more powerful and lasting impact on child development than postnatal exposure.


METHODS
We used generalized linear mixed models with random intercept and slope to analyze the pattern of lead effect of the cohort from pregnancy through 10 years of age on child IQ from 6 to 10 years. We statistically evaluated dose-response nonlinearity.


METHODS
A cohort of 175 children, 150 of whom had complete data for all included covariates, attended the National Institute of Perinatology in Mexico City from 1987 through 2002.


METHODS
We used the Wechsler Intelligence Scale for Children-Revised, Spanish version, to measure IQ. Blood lead (BPb) was measured by a reference laboratory of the Centers for Disease Control and Prevention (CDC) quality assurance program for BPb.


RESULTS
Geometric mean BPb during pregnancy was 8.0 microg/dL (range, 1-33 microg/dL), from 1 through 5 years was 9.8 microg/dL (2.8-36.4 microg/dL), and from 6 through 10 years was 6.2 microg/dL (2.2-18.6 microg/dL). IQ at 6-10 years decreased significantly only with increasing natural-log third-trimester BPb (beta=-3.90; 95% confidence interval, -6.45 to -1.36), controlling for other BPb and covariates. The dose-response BPb-IQ function was log-linear, not linear-linear.


CONCLUSIONS
Lead exposure around 28 weeks gestation is a critical period for later child intellectual development, with lasting and possibly permanent effects. There was no evidence of a threshold; the strongest lead effects on IQ occurred within the first few micrograms of BPb.


CONCLUSIONS
Current CDC action limits for children applied to pregnant women permit most lead-associated child IQ decreases measured over the studied BPb range.
Schnaas
Lourdes
L
National Institute of Perinatology, Mexico City, Mexico.
Rothenberg
Stephen J
SJ
Flores
Maria-Fernanda
MF
Martinez
Sandra
S
Hernandez
Carmen
C
Osorio
Erica
E
Velasco
Silvia Ruiz
SR
Perroni
Estela
E