While many questions about the safety of IVF remain unanswered, one thing is clear: the most effective way to make it safer is to reduce the number of multiple births. While many would-be parents are delighted by the prospect of twins or triplets, the risks for both mother and children are much greater.
Some researchers are now claiming that pre-implantation genetic diagnosis could help reduce multiple births. A team led by Maria Oter at Reprogenetics LLC in San Franciso compared 108 IVF cycles in which PGD screening for chromosomal abnormalities was used to select just one or two embryos for transfer, with 108 standard IVF cycles, where three or four embryos on average were transferred. The women in both groups were of a similar age.
With PGD, the implantation rate per embryo transferred was 24 per cent, double that for standard IVF. So despite transferring fewer embryos 鈥� and thus reducing multiple births 鈥� the pregnancy rate in both groups was similar, Oter reported last week. 鈥淧GD for [chromosomal abnormalities] should become routine for patients over 35,鈥� says Jacques Cohen, scientific director of Reprogenetics.
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However, PGD is not cheap and not everyone is convinced that it boosts pregnancy rates (New 杏吧原创, 12 June, p 6). And Sweden鈥檚 experience suggests that multiple births can be reduced without using PGD. In January 2003, its health department decreed that single embryo transfer should be the norm. Pia Saldeen of the private Cura IVF Clinic in Malm? reported that since the ban, the rate of multiple births at the clinic has dropped from 22 per cent to 6 per cent (compared with an average 36 per cent in the US). Crucially, after 1664 cycles, the pregnancy rate per cycle has remained around 30 per cent. Clinics in Australia have reported similar results with single embryo transfer but the Swedish study is the largest so far.
鈥淭he fear of a reduced overall pregnancy rate did not appear to be justified,鈥� says Saldeen. She believes single transfer should become the norm everywhere. 鈥淔or most patients you don鈥檛 need to transfer two.鈥�