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We read with great interest the article by Mannes et al., which
related the adverse effects of ambient air pollution on birth weight.
That article well described the effects of pollutant exposure on the risk
of low birth weight using a marker of small for gestational age (SGA).
However, that study presents some shortcomings.
First, gestational week at birth is obstetrically and sociall...
First, gestational week at birth is obstetrically and socially a more
important marker for infancy and childhood than birth weight. In recent
studies such as Mannes�f, the gestational week at birth or both the
gestational week at birth and birth weight are used rather than birth
weight. We are convinced that the gestational week should be
incorporated into their methods as an appropriate marker. Secondly, almost
all infants in multiple gestations are SGA even if the pregnancy course is
uneventful. Accordingly, Mannes et al. were compelled to exclude
multiple gestations from the study materials. Finally, the blood-placental
barrier prevents various materials from passing through to the fetus in a
similar manner to that of the blood-brain barrier. Accordingly, it is
inferred that those materials do not easily reach the fetus even if they
can reach to the mother. Mannes et al.�fs study would have been better
researched and more useful if the above problems had been addressed in
their discussion section.
1) Mannes T, Jalaludin B, Morgan G et al. Impact of ambient air
pollution on birth weight in Sydney, Australia. Occup Environ Med
2) Cunningham FG, Leveno KJ, Bloom SL et al. Williams Obstetrics (22nd
edn) TX, McGraw-Hill 2005
3) Wiles NJ, Peters TJ, Leon DA et al. Birth weight and psychological
distress at age 45-51 years: results from the Aberdeen Children of the
1950s cohort study. Br J Psychiatry 2005;187:21-8.