Clinics may be retrieving far too many eggs from IVF patients, a new study suggests.
Researchers say studies indicate the optimal and safe number of oocytes – immature eggs – needed for achieving an ongoing pregnancy is between six and 15.
However, the use of egg freezing, frozen embryo replacement (FER) cycles and aggressive stimulation regimes has increased this number to boost success rates in older women and in those who produce fewer eggs.
The impact of numbers of eggs retrieved and of over-stimulation practices on the health of patients, and on their emotional and financial well-being, is not known.
Details of the analysis were presented at the virtual Annual Meeting of the European Society of Human Reproduction (ESHRE) by Dr Gulam Bahadur from North Middlesex University Hospital, London, who said the results may well reflect global practices, too.
Based on the number of eggs extracted versus IVF cycles, the findings indicate a total of more than 1.625 million eggs in the UK were retrieved from 147,274 women between 2015 and 2018.
While an average of 11 eggs was collected per patient, 16% of cycles were associated with 16-49 oocytes retrieved (per cycle), and 58 women each had more than 50 eggs collected in a single egg retrieval procedure.
Dr Bahadur said: “Our observations suggest that the high oocyte number per retrieval procedure needs re-evaluation.
“In particular, this needs to focus on the side-effects, including ovarian hyperstimulation syndrome and procedure-related complications, and on the fate of unused frozen oocytes and the costs associated with freezing them.
“Patients should be advised that it’s better to collect fewer eggs leading to good quality embryos which may go to term and result in a healthy baby.”
The report is based on all UK IVF clinics and relates to non-donor fertility treatment carried out between 2015 and 2018.
According to the research, during this time 172,341 fresh oocyte retrieval cycles took place.
All outcomes and patterns remained uniform over the four years.
A sizable number of cycles (10,148) did not yield any oocytes, the research found.
More than half (53%) of all IVF cycles were in the desired egg yield range of six-15, a quarter of cycles yielded one to five eggs, 14% produced 16-25, and 2% resulted in 26-49 oocytes.
Researchers point out that multiple birth rates increase significantly from six to 15 oocytes onwards, which presents a risk to patients and babies such as birth complications and low birth weight.
The study found that a total of 931,265 embryos resulted from all eggs retrieved – a fertilisation rate of 57%.
Of the embryos created, more than one in five (22% or 209,080) were transferred into the uterus, while a slightly higher proportion (24% or 219, 563) were frozen.
The fate of the unfertilised oocytes (43%) is unknown, but they are likely to have been discarded, as is normal practice.
Most of the embryos not transferred (54%) will likely be discarded after patients have paid for several years of maintaining them in storage, researchers say.
Dr Bahadur said: “This comes with a financial and emotional cost.
“Patients build an attachment with this frozen material and there’s insufficient counselling to support them.
“They should be given more information about the implications of freezing eggs and embryos.”