NEW YORK (Reuters Life!) - Women living near major, heavily-trafficked roads were more likely to give birth prematurely, perhaps due to traffic-related air pollution, according to a Japanese study.
But Takashi Yorifuji, of the Okayama Graduate School of Medicine, and his team said it was still too early to see a clear link, while other medical experts said noise pollution might also be a factor.
In the study, published in "Epidemiology," Yorifuji and his colleagues studied more than 14,000 babies born between 1997 and 2008 in Shizuoka, about 150 km (94 miles) west of Tokyo, obtaining detailed records on each pregnancy and how close to major roads the mothers lived.
"Air pollution is considered to be a potentially important risk factor of preterm births," Yorifuji told Reuters Health in an e-mail.
Overall, 15 percent of women living within 200 meters of a major road gave birth before 37 weeks, compared to 10 percent of those living further away. A normal pregnancy is 40 weeks.
Other factors have been tied to preterm birth as well, such as age, job, and smoking. But even after accounting for those, the research team found a 50 percent increase in preterm births among women living next to highly trafficked thoroughfares.
These women also had a higher risk of delivering before 32 and 28 weeks. Very premature births carry an especially heavy public health burden.
"In addition, we found a higher risk in housewives than outside workers, and housewives would probably spend more time at home during their pregnancy, and reflect more accurate exposure," Yorifuji added.
Women living close to busy roads also had about double the risk of both high blood pressure and early rupture of the membranes surrounding the fetus, both potential causes of prematurity.
Other exports said the findings squared with previous studies linking air pollution to high blood pressure and inflammation, which could lead to premature rupture of the membranes.
"Everybody always worries that it's not really living by busy roadways, but that it's other things that makes these mothers different," said Beate Ritz of the University of California, Los Angeles, who reviewed Yorifuji's study for publication.
"After all the adjustments, the effect was still there," she added, noting that noise pollution also couldn't be ruled out.
So what should a pregnant woman do if she lives under an expressway or a block from a national highway?
Yorifuji recommended that a pregnant woman who can't avoid living near a busy highway -- often unavoidable in densely populated Japan -- might want to reduce the time she is active outside, along with cutting out smoking and improving her diet.
Others said that studies have shown that it is common for women to move during pregnancy, and that if possible they should consider moving away from busy roads.
Reporting by Lynne Peeples at Reuters Health; editing by Elaine Lies