The time a woman conceives may have an impact on the academic performance of her child, according to a new study reported this week at the Pediatric Academic Societies’ annual meeting.

The study compared for their standardized test scores 1,667,391 Indiana students in grades 3 through 10 who were grouped based on the month in which they were conceived.

Researchers found that those who were conceived any time during the period between May and August performed significantly worse on math and language tests than children who were conceived in other months of the year.

The authors of the study blamed the worse performance on the mothers' exposure to the environmental pollutants, namely pesticides and nitrates during the summer months.

The association was still significant even after other factors such as race, gender, and grade levels were considered.

According to Dr. Paul Winchester of Indiana University School of Medicine who led the study, the lower test scores were already linked with higher levels of pesticides and nitrates in the surface water during the same period.

"Exposure to pesticides and nitrates can alter the hormonal milieu of the pregnant mother and the developing fetal brain," Winchester was quoted by Reuters as explaining in a statement.

Exposure to pesticides and nitrates has already linked to low thyroid hormone levels, or hypothyroidism in pregnant women, which lowers intelligence test scores in offspring.

Although the association does not mean that exposure to pesticides and nitrates definitely leads to lower test scores in children.   But the possibility exists, the authors suggest.