9．Dangers await babies with altitude 高海拔的婴儿有危险

Women who live in the world's highest communities tend to give birth to under-weight babies, a new study suggests. These babies may grow into adults with a high risk of heart disease and strokes.

Research has hinted that newborns in mountain communities are lighter than average. But it wasn't clear whether this is due to reduced oxygen levels at high altitude or because their mothers are under-nourished — many people who live at high altitudes are relatively poor compared with those living lower down.

To find out more, Dino Giussani and his team at Cambridge University studied the records of 400 births in Bolivia during 1976 and 1998. The babies were born in both rich and poor areas of two cities: La Paz and Santa Cruz. L Paz is the highest city in the world, at 3.65 kilometers above sea level, while Santa Cruz is much lower, at 0.44 kilometers.

Sure enough, Giussani found that the average birthweight of babies in La Paz was significantly lower than in Santa Cruz. This was true in both high and low-income families. Even babies born to poor families in Santa Cruz were heavier on average than babies born to wealthy families in lofty La Paz. "We were very surprised by this result," says Giussani.

The results suggest that babies born at high altitude are deprived of oxygen before birth. "This may trigger the release or suppression of hormones that regulate growth of the unborn child," says Giussani.

His team also found that high-altitude babies tended to have relatively larger heads compared with their bodies. This is probably because a fetus starved of oxygen will send oxygenated blood to the brain in preference to rest of the body.

Giussani wants to find out if such babies have a higher risk of disease in later life. People born in La Paz might be prone to heart trouble in adulthood, for example. Low birthweight is a risk factor for coronary heart disease. And newborns with a high ratio of head size to body weight are often predisposed to high blood pressure and strokes in later life.

一个新的研究表明住在世界高海拔地区的女人通常生下体重不足的婴儿。这些婴儿在长大成人后得心脏病和中风的风险很大。

研究暗示在山区出生的新生儿低于平均体重。但是还不清楚这是由于在高海拔的地方氧气不足，还是由于他们的母亲没有获得足够的营养——许多住在高海拔地方的人相对都比住在低处的人穷。

为了了解更多的情况，剑桥大学的迪诺·吉萨尼和他的团队研究了1997年到1998年玻利维亚的400个新生儿的记录。这些婴儿出生于两个城市的富有和贫困地区：拉帕兹和散塔克鲁兹。拉帕兹是世界上最高的城市，海拔3.65千米，而散塔克鲁兹低很多，海拔440米。

当然，吉萨尼发现拉帕兹的新生儿的平均出生体重明显低于散塔克鲁兹的新生儿。无论高收入家庭还是低收人家庭都是如此。甚至散塔克鲁兹的贫穷家庭的婴儿比拉帕兹的富有家庭的婴儿平均体重还要重。吉萨尼说：“我们对这个结果感到吃惊。”

这个结果表明在高海拔出生的婴儿出生前就缺氧了。吉萨尼说：“这可能会触发调节未出生儿成长的荷尔蒙的释放或抑制。”

他的团队还发现高海拔的婴儿通常有相对身体来说较大的头部。这可能是因为一个缺乏氧的胚胎会首先把充氧的血液输送到脑部，然后才送到身体的其他部位。

吉萨尼想要查出这样的婴儿在今后的生活中是不是更容易得病。例如在拉帕兹出生的人在成年之后更可能得心脏病。低出生体重是得冠心病的一个危险因素。头部相对身体较大的新生儿在今后的生活中通常更容易得高血压和中风。

★1).According to the passage, one of the reasons why newborns in mountain communities are underweight is that their mothers are underweight.-W

★2).Giussani’s team members are all British researchers and professors from Cambridge University.-N

★3).Giussani did not expect to find that the weight of a baby had little to do with the financial conditions of the family he was born into.-R

★4).The weight of a newborn has to do with the supply of oxygen even when he was still in his mother’s womb.-R

★5).High-altitude bodies have heads that are larger than their bodies.-W

★6).High altitude babies have longer but thinner limbs than average-N

★7).Giussani has arrived at the conclusion that babies in high-altitude regions are more likely to have heart trouble when they grow up.-W