2014年经济学人 多胞胎 多胞胎怀孕率的减少是件好事（在线收听）

Multiple births

Oh, baby

A reduction in multiple-birth pregnancies is a good thing

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.

This is largely a result of a new policy adopted by the Human Fertilisation and Embryology Authority (HFEA), a regulator.

In 2009 it launched the elective single-embryo transfer policy (now part of its multiple-births minimisation strategy) with the aim of reducing overall IVF multiple pregnancies from 27% in 2008 to 20% initially.

HFEA’s latest figures, dating from 2012, show that the rate has slowed to 18%. The current target is 10%.

According to the HFEA, multiple-birth pregnancies carry a higher risk of premature delivery and children having disabilities as well as late miscarriage, high blood pressure and pre-eclampsia for expectant mothers.

At least that risk is now being tackled for IVF users.