If you are young, healthy and have a good chance of conceiving after IVF, you are at greatest risk of a multiple pregnancy.
Compared with singletons, twins are 4 times more likely to die in pregnancy, 7 times more likely to die shortly after birth and 6 times more likely to have cerebral palsy.
Up to half of all multiple pregnancies result from fertility treatment; around a quarter of all twins and most triplets are born following IVF treatment.
A new baby brings its own joys as well as its own stresses. Many people find that having two or more babies can prove to be an unexpectedly difficult experience.