Miscarriage risk linked to low IVF success
Women who produce fewer eggs during IVF treatment are more likely to miscarry, research suggests.
Scientists analysed 124,351 IVF pregnancies between 1991 and 2008.
About 20% of pregnancies in women who produced fewer than four eggs after the ovarian stimulation phase of IVF ended in miscarriage.
The research indicated the quality of the eggs in these cases was poorer - clinicians said this information would help them to counsel patients.
IVF involves stimulating a patient's ovarian cycle, extracting eggs from their ovaries, fertilising them with sperm in a laboratory, then transferring the embryo into the womb to develop.
Ovarian surgery risk
In the study, carried out at King's College London and the University of Birmingham, the miscarriage rate fell to 15.5% for women who produced between four and nine eggs, and 13.8% for those with between 10 and 14 eggs.
The average risk of miscarriage across the population is 15%.
The co-author of the research, Dr Sesh Sunkara from the Reproduction Unit at King's College London, said: "I think the information will empower women.
"IVF treatment can be a distressing experience, and miscarrying makes it even more agonising."
Dr Sunkara said the study could indicate new risk factors such as ovarian surgery, which could increase miscarriage risk if it lowered the number of eggs a woman produced.
The fact women with fewer eggs had more miscarriages indicated the quality of the eggs must be lower, she said, as it was through such eggs miscarriages happened.
Prof Neil McClure, professor in obstetrics and gynaecology at Queen's University, Belfast, said: "This study is vast in terms of its numbers, and reached a very logical conclusion."
He said reduced egg production was linked to a woman's age, as young women produced lots of healthy eggs, which decreased in number and quality with age.
Prof McClure said he thought the younger women in the study who produced fewer eggs did so because they were on the brink of an early menopause, which was "more common than we might think".
Women who had miscarried after IVF and were worried about miscarrying again could opt for an egg donor, he said, adding that cutting down on smoking and eating a healthy diet would also help.
Help for clinicians
Prof Siobhan Quenby, professor of obstetrics at the University of Warwick, said: "It [the study] will be very helpful for me as I see a lot of people who have miscarried after IVF."
She said uncovering the link between low numbers of eggs and egg quality was important to inform people in deciding whether to carry out another round of IVF, which costs on average about £10,000 if done privately, or opt for an egg donor.
Prof Quenby added: "There is a lot of emotional trauma involved in miscarrying after IVF. It is really devastating for women who wait 10 years to have a baby and then with eight weeks to go they miscarry.
"You want to cry with them."