【经济学人】优生优育：更多证据表明肥胖与剖宫产有关 [英国媒体]

Better childbirth

优生优育

More evidence for a link between Caesarean sections and obesity

更多证据表明肥胖与剖宫产有关

Bugs picked up at birth are good for you

出生时沾染细菌对你有好处



ROUGHLY one human pregnancy in ten presents complications (for example, breech presentation) that might justify the baby being delivered by Caesarean section. In some places that is not possible, and mother and infant have to take their chances with a normal delivery. 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.，

人类妊娠约有20%会出现并发症（如臀先露），这也许证明剖宫产是有道理的。有些地区无法进行剖宫产，能否正常分娩全凭运气。但反之亦然，选择性剖宫产正变得越来越普遍。在巴西、意大利、伊朗，40%以上的孩子以这种方式出生。

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. 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. 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. A study published in Science Advances this week, by Maria Dominguez-Bello at New York University School of Medicine, speaks to the latter hypothesis.

这种紧张昂贵的手术多数在没有绝对必要的情况下进行，长期以来一直令人担忧。但最近又有新的担忧，剖宫产使婴儿无法从母体的阴道和会阴处沾染细菌，正常情况下，细菌在新生儿的肠道内落地生根，有利于改善婴儿未来的健康。越来越多的证据突显出三大问题：剖宫产婴儿容易过敏（免疫系统对不当刺激作出反应，例如坚果蛋白），易患自身免疫病（免疫系统攻击体细胞，例如1型糖尿病），容易肥胖。本周，纽约大学医学院的玛丽•多明戈斯-贝罗在《科学进步》杂志上发表的研究报告证明了最后一点。

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. 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. Since testing the distinction on people, though easy, would be unethical, Dr Dominguez-Bello turned instead to mice. She permitted some pregnant rodents to give birth naturally, while performing antibiotic-free Caesareans on others. She then raised the pups in identical conditions.

肥胖与肠道内的细菌类型有着密切关系，这可能解释了剖宫产为何与肥胖有关。但导致该问题可有两种方式：手术本身隔离婴儿与细菌；手术通常使用大量抗生素。虽然用人体测试区别并不难，但这样做违反伦理，所以多明戈斯-贝罗博士改用老鼠。她让一部分妊娠老鼠自然分娩，给其他老鼠做无抗生素剖宫产，然后让幼崽在相同环境下长大。

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. 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. The probability of this difference resulting from chance is less than one in 1,000. 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.

她的样本数量不多，只有13只妊娠雌鼠，生产了69只幼崽，其中35只为自然分娩，34只剖宫产分娩。但试验得出了明确结论，自然分娩的幼崽长到15周时，平均体重39克，剖宫产分娩的幼崽平均体重45克。偶然造成这种差异的可能性小于千分之一。另外，多明戈斯-贝罗博士检查老鼠的肠道细菌时发现，自然分娩的幼崽有正常的混合细菌，而剖宫产的幼崽缺少拟杆菌、瘤胃菌、梭菌，它们都与苗条身材有关。

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. Fortunately, as Dr Dominguez-Bello points out, this should be an easy problem to fix. 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. It might sound distasteful. But if it works it will give Caesarean babies a better start in life.

看来在老鼠乃至有可能在女性体内，手术本身而非抗生素导致了细菌介导型肥胖。幸运的是，多明戈斯-贝罗博士指出该问题应该很容易解决。她正在试验当剖宫产的婴儿出生不久时，马上用沾染过母亲阴道的棉签擦拭婴儿脸部，设法把相关细菌传染给婴儿。这可能令人厌恶，但如果有效的话，能给剖宫产婴儿一个更好的人生开端。