14 DAY TRIAL // Couples undergoing IVF are struggling for years to have a baby and when this happens, it comes in a number bigger than 1, in at least 40 % of the cases. In fact, the latest cases of sextuplets are the result of IVF treatments.
But the issue is that multiple pregnancies have worse outcomes and in many cases these babies are born prematurely and over 100 of them die annually only in UK, not mentioning the fact that the mother's health is at risk. These pregnancies are multiple mostly because several embryos are transferred to increase the chance of a successful pregnancy.
But a Japanese team has shown that IVF increases the risk of a twin pregnancy even when just one embryo is transferred. The IVF process seems to stimulate embryos to split into identical twins.
Scientists have been trying to develop the embryo for longer in the lab, up to the blastocyst stage when the embryo appears like a multicell ball, before inserting it to the uterus to increase the chance of implantation, as a way to cut down twin rates.
A team led by Dianne Payne at the Mio Fertility Clinic employed special "time-lapse" computer software to see minute by minute what happened to single IVF embryos as they developed in the lab. 2 out of 26 blastocysts displayed clear signs that they could split into identical (monozygotic) twins: two distinct inner cell masses (ICMs). This could have been induced by changes in the lab, called blastocyst collapse, directly linked to IVF.
"It may happen because we are keeping the embryo in culture for longer until it has reached the blastocyst stage. And the formation of two ICMs during blastocyst development may be the cause of the high twin rate after extended culture. It should be possible for doctors to examine embryos before transplantation and advise patients about any potential twinning risk," said Payne.
"The use of blastocyst transfer is increasing as we are being pushed towards elective single embryo transfer to reduce multiple pregnancies. Although it is not the major contributor to twinning, it is important and we need to monitor this outcome." said Richard Kennedy, chairman of the British Fertility Society.
"This new work raises concerns about the possible selection of single later stage embryos for transfer as this might increase the risk of identical twins. The outcome for identical twins is worse than that for non-identical twins." said Professor Alison Murdoch, professor of reproductive medicine at the Newcastle Fertility Centre At Life.
"For the future, collapse rates could be used as a marker to improve our culture environments which will reduce twinning whilst at the same time improve pregnancy rates." said Dr Laurence Shaw, a fertility expert at the London Bridge Fertility Center.