Bath Fertility

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How to interpret IVF success rates

The Human Fertilisation and Embryology Authority (HFEA) – our regulatory authority – requires all clinics to provide information about treatment outcomes which are then verified and published on the HFEA website. These are available to anyone who wants to check a clinic’s performance.

In the past pregnancy rates were published annually in a handbook, which was eagerly pounced on by the Press who would then produce “League Tables” of the ‘Top Ten’ IVF clinics for the next days’ papers. Unfortunately, it proved to be possible to manage the data deliberately to enhance rankings, and the handbook was scrapped in favour of regularly updated digital postings; annual League Tables have now disappeared. It is however, still possible to research individual clinic results site by site here https://www.hfea.gov.uk/choose-a-clinic/

The HFEA now report “births per embryo transferred” because they consider it the best measure of a clinic’s success and say it allows people to make a fair comparison between clinics.

Q: Do “pregnancy rates” accurately reflect a clinic’s performance?

A: By and large the answer is yes, but outcome measures can still be affected by clinic practices.

Q: How?

A: A simple way to do this is to replace multiple embryos: more embryos = more implantations = more pregnancies. The problem with this practice is that the pregnancy rate is only increased a bit, but the multiple birth rate is increased a lot, and this is associated with an increase in risks of prematurity, low birth weight and perinatal mortality.

The HFEA has tried to overcome this tendency by setting targets for reduced multiple births. The current target is 10% for multiple pregnancy rate (MPR) and has been for a few years now.

We have had an MPR less than 10% for the last five years, but many clinics have still failed to achieve this.

As Obstetricians we often look after the patients we have treated, and so we are very aware that multiple pregnancies are not always easy – we therefore feel it is more ethical to promote single embryo transfer to avoid the unnecessary risks that multiple pregnancies can have.

Each clinic has to provide the MPR, and it can be found in any clinics’ data if looked for. Improvements in embryo freezing, resulting in good pregnancy rates means that there is less need to transfer multiple fresh embryos, and our ethos is “One healthy baby at a time”. We think this is the best practice.

Q: Are there other things that affect pregnancy rate?

A: Yes – ovarian reserve has an effect: Patients with lower ovarian reserve produce fewer eggs, which can reduce the pregnancy rate. It is possible to use strategies to avoid inclusion of this group in a clinic’s data. We believe everyone has a chance of a pregnancy, as long as they have some eggs left in their ovaries. We won’t give false hope, but we will be ‘up front’ if chances are low. We do however discourage women over 43 years old from attempting IVF, as the pregnancy rate is virtually zero by this time, and whilst eggs may be recovered and fertilised, unfortunately pregnancies rarely follow in this older age group.

Q: So, how can I be sure that my clinic is giving me a good chance of having a healthy baby?

A: Look at the pregnancy rate for your age group and compare to the national norm, as well as other clinics that interest you. Look at the multiple birth rate, is it as low as it should be, remember healthy babies, one at a time, is best.

Look at the frozen embryo pregnancy rate for your age group – if it’s good, then your frozen embryos will be safe for future use if needed, and your clinic will look after them well. Remember that pregnancy rate is only one measure of a clinic’s treatment, and your health and especially your baby’s health with a safe pregnancy is what really counts.