One limitation of this study was the relatively short period (22 months) for which air toxics and speciated PM2.5 monitoring data were available, leading to moderate-to-strong negative correlations between first and third trimester measures for many pollutants and strong positive correlations between second trimester and entire pregnancy averages for almost all pollutants.
In models combining all three trimester measures and using standardized coefficients, the effect of first-trimester maternal plasma lead was somewhat greater than the effect of first-trimester maternal whole blood lead and substantially greater than the effects of second- or third-trimester plasma lead, and values averaged over all three trimesters.
Fetal growth measurements include head circumference and abdominal circumference in the second trimester measured to the nearest millimeter by using standardized ultrasound procedures.
In conclusion, we found that first-trimester measures of fetal lead exposure particularly levels of lead in maternal plasma, but also levels of lead in maternal whole blood were predictive of adverse neurodevelopment later in life, with an effect that was independent from that of postnatal lead exposure and that was stronger than the effects associated with second- or third-trimester measures.
Although potential mechanisms are uncertain, associations with first-trimester measures are consistent with hypotheses involving epigenetic changes, because such effects have been observed to be more frequent for periconceptional than for later exposures (Lee et al. 2009; Tobi et al. 2009).
Furthermore, first trimester urinary measures may not be representative of exposure during critical windows of immune system development.
Our results are based on the second and third trimester ultrasonography measures in combination with birth outcomes.
Established risk factors included age, BMI, diabetes duration, parity, history of preeclampsia, smoking status, and second trimester clinical measures such as systolic blood pressure, diastolic blood pressure, HbA1c, and ratio of urine albumin to creatinine.
Even though all trimester-specific measures correlated moderately with entire pregnancy averages (r ≥ 0.46), second-trimester exposure averages correlated most strongly with entire pregnancy averages (r ≥ 0.80), and first- and third-trimester averages for the same pollutants were least correlated (r = 0.05 0.37) (results not shown).
In the second trimester, doctors measure abdominal circumference, and check the chambers of the heart, the kidneys and bladder to spot defects and monitor growth.
First, we report here the largest prospective cohort of pregnant women with first assessment at the 1st trimester and measured adiponectin levels that we are aware of.
