第一段

ROUGHLY one human pregnancy in ten presents complications (for example, breech presentation) that might justify the baby being delivered by Caesarean section. 人类的怀孕大概有十分之一的比例表现出并发症从而符合剖腹产的指征，如臀位。

科普：适合顺产的是头位，也就是胎儿头朝下对着宫颈口。臀位是臀朝下，不易顺产。

In some places that is not possible, and mother and infant have to take their chances with a normal delivery. 在一些没有剖腹产条件的地方，孕妇和胎儿要冒险尝试正常的分娩。take a chance with, 冒险尝试做某事。

科普：顺产的确是冒险，虽然没有可靠统计，在古代，由于医学不发达，产妇分娩的死亡率是十分之几。

But the opposite is also true. Elective Caesarean is becoming more and more common. In Brazil, Italy and Iran more than 40% of children are born this way. 相反的事例也是真的。产妇选择剖宫产越来越普遍。在巴西、意大利和伊朗，超过40%的婴儿通过剖腹产出生。

第二段

That a stressful and expensive procedure is being conducted more often than is strictly necessary has long been a concern. But, more recently, a second worry has emerged. 一个紧张而昂贵的流程被超过必要得执行（剖腹产手术）引起了关注。但是，进来，另一个担忧出现了。

This is that Caesarean section stops infants picking up, from their mother’s vaginas and perineums, bacteria that would normally establish themselves in a newborn’s gut, and by doing so improve its future health. 这是因为剖腹产手术让婴儿们避免了接触母亲阴道和会阴部位的细菌，这些细菌本来会着床于婴儿的肠道，能在未来改善孩子的健康。

Accumulating evidence suggests three things, in particular. These are that Caesarean babies are more prone than others to allergies (in which the immune system responds to inappropriate stimuli, such as nut proteins), to autoimmune diseases (in which the immune system attacks body cells, as happens in type-1 diabetes), and that they are also more likely to become fat. 越来越多的证据特别显示了三件事：剖腹产出生的婴儿更容易过敏（免疫系统对不恰当的刺激，如坚果的蛋白，做出反应），更容易患自身免疫类疾病（免疫系统攻击自身细胞，如I型糖尿病），更容易肥胖。

A study published in Science Advances this week, by Maria Dominguez-Bello at New York University School of Medicine, speaks to the latter hypothesis.由纽约大学医学院的Maria Dominguez-Bello发表在Science Advances杂志上面的一项研究提出了以上假设。

第三段

A connection between obesity and the types of bacteria living in someone’s gut is well established, and thus seems the likely explanation for the link between Caesareans and obesity. 肥胖和人的肠道菌落类型的联系已经被确认，所以它也解释了剖腹产和肥胖之间的联系。

But this could come about in one of two ways. Either the procedure itself keeps baby and bacteria apart or the large amounts of antibiotics which usually accompany the surgery are responsible. 但是这种结果可能是一种或者两种路径造成的，或者是剖宫产过程中隔离了胎儿和细菌，或者是在由于进行了手术而使用的大量抗生素消灭了细菌。

Since testing the distinction on people, though easy, would be unethical, Dr Dominguez-Bello turned instead to mice. 虽然想要了解两者的差别很容易，但是有悖于伦理，所以 Dominguez-Bello博士选择用小白鼠做实验。

She permitted some pregnant rodents to give birth naturally, while performing antibiotic-free Caesareans on others. She then raised the pups in identical conditions. 她让一些小白鼠正常分娩，同时让另一些用无抗生素的方式剖宫产。之后她把幼崽在同样的条件下养殖。

科普：用人做有没必要的风险的医学实验是有悖于伦理的，比如不用抗生素的分娩容易引起感染。

第四段

Her sample was not large—a mere 13 pregnant females produced 69 offspring, of which 35 were born naturally and 34 were delivered by Caesarean. 她的样本数不大，只有13只怀孕的母老鼠，生了69只幼崽，其中35只顺产，34只剖腹产。

But her results were conclusive. At 15 weeks of age, pups that had been delivered naturally weighed an average of 39 grams. Their Caesarean-delivered kin averaged 45 grams. 但是她的结果是确定的。15个星期后，顺产小白鼠幼崽的平均体重是39克，而剖腹产小白鼠幼崽的是45克。

The probability of this difference resulting from chance is less than one in 1,000.在自然条件下，这种事情的概率是千分之一以下。

Moreover, when Dr Dominguez-Bello examined the gut bacteria of her mice she found that those born naturally had a normal mixture while those born via Caesarean lacked Bacteroides, Ruminococcaceae and Clostridiales. These are all groups associated with lean bodies. 此外，当Dominguez-Bello检查小白鼠幼崽的肠道菌落时，她发现顺产的小白鼠有正常的菌落群，而剖腹产的小白鼠缺少拟杆菌、瘤胃菌和梭菌属的细菌。这些细菌都和瘦有关。

第五段

It seems, then, that in mice—and by extension presumably in women—it is the operation itself rather than the associated antibiotics that are promoting bacteria-mediated obesity. 在小白鼠试验中，可能是手术本身而不是手术中的抗生素导致了细菌媒介引起的肥胖。这个结论可以扩展至人类。

也就是说，人类的剖腹产导致婴儿无法解除某些菌落，从而引起肠道菌落失调，导致肥胖。

Fortunately, as Dr Dominguez-Bello points out, this should be an easy problem to fix. 幸运的是，如Dominguez-Bello指出的，这个问题很容易搞定。

She is now experimenting with taking a swab of the mother’s vagina and wiping it on an infant’s face shortly after a birth by Caesarean, to try to pass on the relevant bugs. 她现在正在实验用棉签蘸取母亲的阴道分泌物在生产后立即涂在婴儿脸上，目的是传播相关的细菌给婴儿。

It might sound distasteful. But if it works it will give Caesarean babies a better start in life. 这种方法听起来很不可思议，但是如果有效，它能给剖腹产的孩子们一个更好的生命之开始。

难点解析

1. ROUGHLY one human pregnancy in ten presents complications (for example, breech presentation) that might justify the baby being delivered by Caesarean section.句子的主干是 one human pregnancy in ten presents complications，后面的that might justify the baby being delivered by Caesarean section部分修饰complications。十分之一的人类怀孕表现出了并发症，什么并发症，符合剖腹产指征的并发症。

2. That a stressful and expensive procedure is being conducted more often than is strictly necessary has long been a concern. But, more recently, a second worry has emerged. That引导的从句表强调。That引导的从句（ stressful and expensive procedure is being conducted more often than is strictly necessary）是句子的主语。剖腹产被滥用引起关注。