Season of conception tied to school performance

The time of year a womanconceivesmay influence the future academic performance of her child, according to research reported this week at the Pediatric Academic Societies' annual meeting.

When researchers linked standardized test scores of 1,667,391 Indiana students in grades 3 through 10 with the month in which each student had been conceived, they found that children conceived May through August scored significantly lower on math and language tests than children conceived during other months of the year.

The correlation between test scores and conception season held regardless of race, gender, and grade level.

Why might this be? According to Dr. Paul Winchester of Indiana University School of Medicine who led the study, the evidence points to environmental pesticides, used most often in the summer months, as a possible player.

The lower test scores correlated with higher levels of pesticides and nitrates in the surface water (nearby streams and other bodies of water) during that same time period, he told Reuters Health.

"Exposure to pesticides and nitrates can alter the hormonal milieu of the pregnant mother and the developing fetal brain," Winchester explained in a statement. For example, past research has linked exposure to pesticides and nitrates to low thyroid hormone levels ("hypothyroidism") in pregnant women and hypothyroidism in pregnancy has been tied to lower intelligence test scores in offspring.

While the current findings do not prove that pesticides and nitrates contribute to lower test scores, "they strongly support such a hypothesis," Winchester said.

"A priori there should be no reasons particularly why the month of conception should change your (test) scores," he added in an interview, "and yet from our chain of evidence our hypothesis was that if pesticides do alter the friendly environment of the developing fetus than that might be reflected in lower scores. And unfortunately that's what we found."

"There is something going on" and it needs to be studied further, Winchester concluded.

在本周举行的"儿科学术协会年会"上，一项研究报告称，母亲怀孕的月份可能会影响孩子以后的学业成绩。

研究人员对印地安那州1,667,391名3到10年级学生的统一考试成绩和他们的受孕月份进行了相关分析。结果发现，与其它月份受孕的孩子相比，5月至8月受孕的孩子的数学和语言成绩要低得多。

考试成绩与受孕季节这一相互关系不受种族、性别和年级的影响。

该如何解释这一结论？本研究的带头人、印第安纳大学医学院的保罗·温彻斯特博士说，罪魁祸首有可能是空气中的杀虫剂，这些杀虫剂在夏季使用得比较多。

他在接受路透社健康部的采访时说，考试低分与地表水（附近的小溪和其它水体）中含量过高的杀虫剂和硝酸盐有关。

温彻斯特解释说，"接触杀虫剂和硝酸盐会使孕妇体内的荷尔蒙环境发生改变，从而影响胎儿的大脑发育。"比如，以往的研究发现，孕妇体内甲状腺激素含量低（甲状腺机能减退）与接触杀虫剂和硝酸盐有关，而怀孕期间甲状腺机能减退又与孩子智商低有关。

尽管目前的研究不能证明杀虫剂和硝酸盐导致考试低分，但是，温彻斯特说，"它们为这一假设提供了有力的支持。"

他在采访中补充道，"我们是这样推理的，既然没有特别的原因来解释受孕的月份影响考试成绩这件事，那么根据一系列的证据，我们假设如果杀虫剂确实影响胎儿成长的良好环境，那么这种影响也许会导致考试低分。不幸的是，这正是我们通过研究发现的。"

温彻斯特最后总结到，"这其中还有一些影响因素"有待进一步的研究。

Vocabulary:
conceive: To become pregnant（怀孕）
hypothyroidism: 甲状腺机能减退