The date that a child is conceived has an impact on both their likelihood for premature birth and their later academic performance, US researchers say.
Seasonal use of pesticides and nitrate fertilisers may be to blame, the Indiana University School of Medicine team add.
The researchers analysed more than 27 million live births in the US from 1996 to 2002.
They found that rates of premature birth in the US were highest in May-June (11.9 percent of live births) and lowest in August-September (almost 10.8 percent). Pesticide and nitrate levels in surface water are highest in May-June, lowest in August-September.
"A growing body of evidence suggests that the consequences of prenatal exposure to pesticides and nitrates as well as to other environmental contaminants is detrimental to many outcomes of pregnancy," researcher Dr Paul Winchester, professor of clinical paediatrics, said in a prepared statement. "As a neonatologist, I am seeing a growing number of birth defects and preterm births, and I think we need to face up to environmental causes."
Timing tied to marks
They also looked at Indiana Statewide Testing for Educational Progress (ISTEP) scores from 1.6 million children in grades 3 through 10. The team compared that with the month the children were conceived.
Children conceived in June through August had the lowest ISTEP scores for math and language, according to the study, presented Monday at the annual meeting of the Paediatric Academic Societies.
"Exposure to pesticides and nitrates can alter the hormonal milieu of the pregnant mother and the developing foetal brain. While our findings do not represent absolute proof that pesticides and nitrates contribute to lower ISTEP scores, they strongly support such a hypothesis," Winchester said. – (HealthDayNews)
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