It’s not clear why, exactly, heavy traffic could cause premature birth. Air pollution from car exhaust could have something to do with it. Some studies have found that women exposed to high levels of carbon monoxide were up to twenty-five percent more likely to have a preterm baby than women in areas with cleaner air. It’s also possible that loud noise from highways and freeways could play a role by disturbing pregnant women’s sleep. Losing sleep typically causes stress, which is linked to premature 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。