Large prospective birth cohort studies on environmental contaminants and child health - goals, challenges, limitations and needs.

The adverse health effects of environmental contaminants (ECs) are a rising public health concern, and a major threat to sustainable socioeconomic development. The developing fetuses and growing children are particularly vulnerable to the adverse effects of ECs. However, assessing the health impact of ECs presents a major challenge, given that multiple outcomes may arise from one exposure, multiple exposures may result in one outcome, and the complex interactions between ECs, and between ECs, nutrients and genetic factors, and the dynamic temporal changes in EC exposures during the life course. Large-scale prospective birth cohort studies collecting extensive data and specimen starting from the prenatal or pre-conception period, although costly, hold promise as a means to more clearly quantify the health effects of ECs, and to unravel the complex interactions between ECs, nutrients and genotypes. A number of such large-scale studies have been launched in some developed counties. We present an overview of "why", "what" and "how" behind these efforts with an objective to uncover major unidentified limitations and needs. Three major limitations were identified: (1) limited data and bio-specimens regarding early life EC exposure assessments in some birth cohort studies; (2) heavy participant burdens in some birth cohort studies may bias participant recruitment, and risk substantial loss to follow-up, protocol deviations limiting the quality of data and specimens collection, with an overall potential bias towards the null effect; (3) lack of concerted efforts in building comparable birth cohorts across countries to take advantage of natural "experiments" (large EC exposure level differences between countries) for more in-depth assessments of dose-response relationships, threshold exposure levels, and positive and negative effect modifiers. Addressing these concerns in current or future large-scale birth cohort studies may help to produce better evidence on the health effects of ECs.

[The extent and relative changes of equities in utilization of prenatal care among women in some areas of China].

OBJECTIVE: To assess the extent and relative changes of the equities in prenatal care utilization among women with different educational attainment in some areas of China. METHODS: Data were collected in 13 counties/cities covered by Perinatal Health Care Surveillance System established by Institute of Reproductive and Child Health, Peking University. The study population consisted of 103 704 women who delivered single live births in 1994 and 2000. Chi-square and multiple logistic regression were employed to compare the systematic management rates and relative risks. Concentration index was used to assess the relative changes of equities in prenatal care utilization. SPSS 11.5 and Microsoft Excel 2003 were used for analysis. RESULTS: The total systematic management rate was 22.1% in 1994 and 57.4% in 2000. The concentration index was -0.046 in 1994 and 0.066 in 2000. In northern areas, the concentration index increased from 0.015 in 1994 to 0.295 in 2000, while it increased from -0.015 in 1994 to 0.062 in 2000 in southern areas. In rural areas, the concentration index increased from 0.002 in 1994 to 0.026 in 2000, while it decreased from 0.042 in 1994 to 0.019 in 2000 in urban areas. CONCLUSION: Inequities in prenatal care utilization in 2000 become more obvious than in 1994, especially in northern areas. More attention should be paid to solve the inequities.