经济学人下载:双胞胎母亲更幸福

Mothers of twins do not just get twice the bundle of joy—they are also healthier than other mothers

拥有双胞胎的母亲不仅能得到双份的快乐，而且她们会比其她母亲更健康。

THROUGHOUT history, twins have provoked mixed feelings. Sometimes they were seen as a curse—an unwanted burden on a family’s resources. Sometimes they were viewed as a blessing, or even as a sign of their father’s superior virility. But if Shannen Robson and Ken Smith, of the University of Utah, are right, twins have more to do with their mother’s sturdy constitution than their father’s sexual power.

在历史上，对待双胞胎有着复杂的感情。有时，他们被视为祸根--家庭中不受欢迎的负担。有时，他们被视为祝福，或作为他们父亲拥有更好的性能力的一个标志。但如果犹他大学的夏侬.罗布森和肯.史密斯是正确的，那么双胞胎为他们的母亲那健壮的体格所做的比为他们的父亲的性能力方面所做的更多。

At first blush, this sounds an odd idea. After all, bearing and raising twins is taxing, both for the mother and for the children. Any gains from having more than one offspring at a time might be expected to be like higher infant and maternal mortality rates. On this view, twins are probably an accidental by-product of a natural insurance policy against the risk of losing an embryo early in gestation. That would explain why many more twins are conceived than born, and why those born are so rare (though more common these days, with the rise of IVF). They account for between six and 40 live births per 1,000, depending on where the mother lives.

乍看之下，这好像听起来好像是一个奇怪的想法，毕竟对于母亲和孩子，生产和抚养双胞胎是很费力的。每次从多于一个孩子那里获得的比期望的更多，通常会伴随着较高的婴儿死亡率和母亲死亡率。根据这种观点，双胞胎很可能是一次在怀孕期间用自然保障方式防止流产的意外的副产品。这样就能解释为何双胞胎怀的比生的多，而且为什么生的会这么少（虽然现在更多的运用试管受精已经很平常）。他们解释说每1000个中成活率在6到40之间，这要根据母亲生活的地方。

Dr Robson and Dr Smith, however, think that this account has got things the wrong way round. Although all women face a trade-off between the resources their bodies allocate to reproduction and those reserved for the maintenance of health, robust women can afford more of both than frail ones. And what surer way to signal robustness than by bearing more than one child at a time? In other words, the two researchers conjectured, the mothers of twins will not only display greater overall reproductive success, they will also be healthier than those who give birth only to singletons.

然而，罗布森博士和史密斯博士认为这个解释是事情处于错误中。尽管许多女人面临着一个权衡，那就是在身体分配给生育所需的资源和保留给保持身体健康所需营养之间权衡。强健的母亲可能比瘦弱的母亲提供的更多。而且能有什么比健壮的母亲生育多于一个孩子更有说服力呢？换言之，这两位调查者推测，双胞胎的母亲不仅更好的展示了整体的生育成功，也会比只生一个孩子的母亲更健康。