IVF practitioners should retrieve around 15 egg cells in a single cycle from hopeful mothers to attain optimum likelihood of live birth, according to a collaborative study by British scientists.
Their statistical analysis was based on data from 400,000 IVF cycles sourced from UK’s fertility treatment regulator HFEA. In its paper published in the journal Human Reproduction, the study revealed that the “best chance of live birth was associated with the number of eggs of around 15 and showed a decline with more than 20 eggs.”
The researchers are suggesting a “strong relationship” between live birth rate and number of cells retrieved in a single cycle. Experts have also warned that this should not indicate that doctors should try and get more and more egg cells.
In one menstrual cycle, an average woman produces one single egg from her ovaries. In technology assisted reproduction like IVF (in-vitro fertilisation) women are injected with certain hormones that stimulate the ovaries to produce multiple oocytes (eggs). These cells are then retrieved and then subjected to fertilisation in the lab (in-vitro) and successful embryos are planted back into the mother’s uterus or surrogate. Over stimulating at the previous step can cause a dangerous condition called OHSS (Ovarian Hyperstimulation Syndrome) that can turn fatal.
“Risking OHSS is considered to be reckless. It can lead to death in its worse form. Poor eggs can arise in overstimulation-also not helpful. Paradoxically, severe OHSS occurs mainly in pregnant patients, so this can lead to miscarriage,” said Samuel Lee, acclaimed clinical embryologist, consultant and academic in London.
Based on IVF outcomes between 2006 and 2007, the predicted live birth rate for women aged 18 to 34 with 15 eggs retrieved was 40pc.
For women aged 35 to 37 having the same number of eggs removed, the birth rate figure dropped to 36pc. It further fell to 27pc for those aged 38 to 39, and 16pc for women over 40.
Instead of focusing on how many cells are to be retrieved, getting good quality oocytes without harming the mother is more important, seems to be the general consensus among IVF experts.
“Quality can be more important than quantity and each case should be reviewed individually,” said Dr. Martyn Blayney, embryologist at Bourn Hall, one of the leading fertility clinics in the market. Fertility treatment centres are popping up on a daily basis, the market for IVF is growing steadily; Bourn Hall itself opened shop in India recently. There is some caution in the air filled with concern that statistical evidence is not dictated into a medical breakthrough by the new crop of fertility practitioners.
Dr Alastair Sutcliff, senior clinical lecturer at University College London said: “There is no need to standardise the number of oocytes to be retrieved. There are lots of other factors to consider like female age, BMI, how effective stimulation is and also male factors.”
The authors of this study came to their conclusions by creating a predictive model and then charting out a mathematical graph called the nomogram. This nomogram shows the relationship between women’s age, the numbers of eggs retrieved and the predicted live birth rate. Tools like this could be combined with current methods to measure a woman’s ovarian reserve and make decisions about how much the ovary needs to be stimulated. This can help in “prediction of success”, added Dr Sutcliff.