IT HAS long been known that in-vitro fertilisation (IVF) increases the chances of multiple births, as several fertilised eggs are implanted in a woman to improve the chances of pregnancy. A fifth of all successful IVF treatments in Britain result in multiple-birth pregnancies, compared with just over 1% from natural conceptions.

Such was the success of IVF after the first test-tube baby was born in 1978 that the rate of all multiple-birth pregnancies rose from ten per 1,000 in that year to 16.4 in 2009. The total number of multiple births doubled during that time. However, for women over 35—frequently users of IVF—it shot up 600%.

When all goes well, a multiple birth can be good news for women who had difficulty conceiving. But it also carries risks: the infant mortality rate is five times higher than for single births. So the fact that newly released statistics show that the number of multiple births has started to fall is welcome.(Economist)

翻译：

众所周知体外受精(IVF)可以增加多胞胎几率，因为要将几个受精卵植入一个女人体内来提高受孕几率。在英国，自然分娩多胞胎的几率仅超过1%，而体外受精的方式则成功的将多胎妊娠的几率提升到1/5。

自1978年第一例试管婴儿出生之后，多胞胎受孕率由那一年的千分之十上升到2009年的千分之16.4，这是体外受精的又一成功。多胞胎的总数在那些年间翻了一倍。但是，对于35岁以上的妇女，即体外受精的常见对象，她们生产的多胞胎总数直线上升了600%。

当一切都顺利的时候，多胞胎对于经历了痛苦艰难治疗的不孕妇女来说无疑是个好消息。但这也同样带来危险：多胞胎的婴儿死亡率比一个婴儿高五倍。最新发布的统计数据显示多胞胎的数量正开始降低，这也算是个好消息。