24 March 2014
ByAppeared in BioNews 747
The findings revealed that women who produce four eggs or fewer during an IVF cycle have a 20 percent risk of miscarrying, but this fell to around 15 percent for women who produced four to nine eggs. Women who produced ten to 14 eggs had a miscarriage rate of just below 14 percent.
Speaking to BBC News, Dr Sesh Sunkara of King's College London, who worked on the study along with researchers from University of Birmingham, said: 'I think the information will empower women, IVF treatment can be a distressing experience, and miscarrying makes it even more agonising'.
It was previously suspected that a poor response to ovarian stimulation in IVF is connected with a higher risk of miscarriage. However, earlier studies have proven inconclusive due to the limited sample numbers included.
Over 400,000 IVF cycles and 124,351 pregnancy outcomes were analysed enabling the researchers to draw strong conclusions from the data. Neil McClure, professor in obstetrics and gynaecology at Queen's University Belfast, who was not involved in the research, said: 'This study is vast in terms of its numbers, and reached a very logical conclusion'.
One of the risk factors for miscarriage is age, but the association with lower egg production in the study remained even when taking this into account. Dr Sunkara suggested that the increase in miscarriages seen could be due to a fall in the quality of eggs produced, with a high proportion of those released having an unviable number of chromosomes.
Professor McClure explained that although the quality of eggs decreases with age, early menopause may explain why younger women respond poorly to ovarian stimulation. Early menopause 'is more common than we may think', he said.
Hyper-response to ovarian stimulation, which has been linked to a lower live birth rate, was also examined. However, no association with over production of eggs and miscarriage was found. The researchers suggested that the lower birth rate could be better explained by a reduced chance of fertilisation due to egg immaturity and poor implantation onto the womb.
The research may enable better counselling of those looking to undertake IVF. Siobhan Quenby, professor of obstetrics at the University of Warwick, said: 'It will be very helpful for me as I see a lot of people who have miscarried after IVF'. Adding that the information may assist patients choosing between secondary rounds of IVF or opting for an egg donor.