ESHRE: How to stop twins in their tracks
One of the pitfalls of having IVF is that you're likely to end up with more than you bargained for - even when only one embryo is implanted, the likelihood of having identical twins runs at roughly seven times that for natural births. Through some ingenious time-lapse film-making, Dianna Payne of the Mio Fertility Clinic in Yonago, Japan, has now shown us how it happens.
She set up a microscope and video camera to document the first few hours and days of a growing test-tube embryo's life. As these still images from the movei show, the embryo on the bottom left clearly features not one, but two 'inner cell masses' - the ball of cells that ultimately becomes a person. PAyne's film showed how, in some cases, the cavity that makes up the rest of the 'blastocoele' sometimes collapses and reforms, occasionally transferring some cells to the opposite side of the embryo and resulting in two cell masses, which then go on to become identical twins.
Payne's work used surplus embryos donated to research. But it has raised hopes that one day, all mothers undergoing IVF could have their embryos examined to check for this process before the embryo is transferred to the womb. Thus couples could avoid having twins... unless they really want them, of course.