A study of the correlation between time spent in the womb and test scores has indicated that the definition of âpremature' may have to be revised.
Researchers have known that babies born premature are at risk for slowed brain development, but a new study suggests that even among those considered "normal term" — between 37 and 41 weeks — a couple of extra weeks in the womb might make a difference later in school test scores.
The study tracked 128,000 New York City public school children who were all considered full-term and checked how they did on third-grade math and reading tests. The majority of children did fine on the tests and suffered no adverse effects from a shorter gestation period, however the group of kids who did poorly contained more of those born at 37 or 38 weeks than those born later.
"Certainly the vast majority of 37-weekers and 41-weekers would end up developing typically," said Dr. Kimberly Noble, the lead author on the new study from Columbia University Medical Center and New York-Presbyterian Hospital in New York.
Women should "at least proceed with caution before electing to have an earlier term birth," said Noble, an assistant pediatrics professor at Columbia University Medical Center.
The study showed that in general children born at 41 weeks scored one point higher on the third grade math and reading tests, which translates to roughly a 1.5 IQ point difference. While this difference is insignificant, there are significant concerns about the lower end of the test-score distribution. Children born at 37 weeks were 33% more likely than those born at 41 weeks to have reading difficulties, and 19% more likely to have problems with math.
"These outcomes are critical and predict future academic achievement," said Naomi Breslau, a Michigan State University professor and sociologist. Her own research has linked lower IQs in 6-year-olds born weighing the same as the average birth weights at 37 and 38 weeks' gestation, compared with those born heavier.
While interesting, the results don't show direct correlation between early-term birth and hampered brain development. The study had no way of controlling for confounding variables such as complications that led to the early delivery and more research will have to be done to isolate the causal factors involved in the hampered brain development of those early-termers struggling academically during childhood.
Of course, many women don't have any control over when they give birth, but the researchers think those who do — such as those who give birth via an elective C-section — should go as far into the normal term of the pregnancy as possible.