If you need yet another reason - beyond wasted gasoline, lost time and road rage - to hate traffic jams, here's one: They're bad for babies.

Columbia University economist Janet Currie and doctoral student Reed Walker explored the impact of traffic - and the resulting pollution - on the weight and prematurity of newborns.

Using data from New Jersey and Pennsylvania, their study examines health statistics for babies born to families living near toll plazas, comparing the data gathered before and after the introduction of E-ZPass, the electronic system that allows motorists to pay tolls without stopping.

The system has been linked to significant reductions in pollution (all that braking and accelerating to toss in your coins adds up).

In their paper "Traffic Congestion and Infant Health," published by the National Bureau of Economic Research, Currie and Walker find that reduced traffic congestion resulting from E-ZPass is linked to a 10.8 percent drop in the incidence of premature birth (defined as less than 38 weeks of pregnancy) and an 11.8 percent reduction in low birth weight (2.5 kilograms or less). These results are for mothers living within two kilometers of a toll plaza; for those living within three kilometers, the declines are smaller but still clear (7.3 percent and 8.4 percent, respectively).

The authors focused on three major tollways - the Pennsylvania Turnpike, the New Jersey Turnpike and the Garden State Parkway - and relied on state birth records from 1997 to 2002 (for Pennsylvania) and 1994 to 2003 (for New Jersey).

They believe their results have national implications, however. Currie and Walker cite an Institute of Medicine study that puts the full costs to society of premature births at $51,600 per infant, and they calculate that roughly 1 million babies could be affected by congestion.

As a result, "nationwide reductions in prenatal exposure to traffic jams could lower the number of preterm births by as many as 10,800 annually, a drop that can be valued at $557 million per year."

And these researchers practice what they preach: "When I drive over the George Washington Bridge or the Lincoln Tunnel," Currie said, "I always use E-ZPass."

Carlos Lozada wrote this piece for the Washington Post.