It’s not clear why, exactly, heavy traffic could causepremature birth. Air pollution from car exhaustcould have something to do with it. Some studieshave found that women exposed to high levels ofcarbon monoxide were up to twenty-five percentmore likely to have a preterm baby than women inareas with cleaner air. It’s also possible that loudnoise from highways and freeways could play a roleby disturbing pregnant women’s sleep. Losing sleeptypically causes stress, which is linked topremature birth. Whatever the specific cause,these studies at the very least suggest that loud, heavy traffic, and pregnancy don’t mix.

　　目前尚不清楚，究竟为什么，交通繁忙可能导致早产的确切原因。从汽车尾气造成的空气污染可能与之有些联系。一些研究发现，暴露在高浓度的一氧化碳中的妇女比在空气清洁的地区的妇女高达早产的可能性高达百分之二十五。公路和高速公路的巨大噪音也有可能会干扰孕妇的睡眠。失眠通常会导致压力，而压力与早产有关。无论具体原因是什么，至少在这些研究表明，发出巨大噪音的繁忙交通应当与孕妇分离。