What’s in a number? Deciphering in vitro fertilisation success rates

IVF is hugely demanding and requires substantial investment of time, energy, emotion and money. With the number of clinics offering assisted reproduction rising in response to increased demand, how do you discriminate between the various success rates and make an informed choice?

Not all success rates are created equal

There is currently no standardised method of measuring success and presenting results, which means you really need to drill down into the data and learn how to interpret often misleading statistics. IVF consists of several stages and problems can arise at any step, so clinics can focus on – or exclude – any one of the following phases in order to favourably present their results:

1. Ovarian stimulation with fertility drugs
2. Egg retrieval
3. Fertilisation and embryo culture
4. Embryo transfer (ET) and implantation
5. Clinical pregnancy
6. Live birth

The final two stages are the primary parameters by which clinics measure success. They can be categorised as follows:

  • Clinical pregnancies per embryo transfer – This is a popular measure of success as it does not include failures during the previous stages (hormone stimulation, egg retrieval and embryo transfer) or any subsequent miscarriages
  • Live births per embryo transfer – This figure is lower than the clinical pregnancy rate due to miscarriage and also varies depending on whether a fresh embryo following hormone stimulation or frozen embryo is used (frozen embryos tend to be more successful as the previous steps in the IVF process are avoided)
  • Live births per started treatment cycle – Denotes how many babies are born following a fresh embryo transfer in one treatment cycle. This figure does not include babies born as a result of frozen embryo transfer (FET)
  • Live births per complete treatment cycle – This cumulative success rate is higher as it includes multiple embryo transfers, both fresh and frozen, from one stimulated cycle. It also includes cycles where all embryos were electively frozen, which is becoming an increasingly popular approach

Don’t judge a clinic by its success rate  

There are a number of factors that can positively or negatively influence success rates and which need to be taken into consideration when crunching the numbers. Make sure you are looking at success rates that correspond closely with your particular situation i.e. if possible, compare the results of women of a similar age and medical background who underwent the particular treatments you are considering.  Egg donation screens out the key variables adversely affecting success rates – maternal age and fertility – and therefore the most accurate indicator of a clinic’s capability is the number of live births using fresh donor eggs.

Key factors influencing success rates:

  • Expertise and experience of physicians – doctors have to oversee a decent number of IVF treatment cycles per year in order to deliver quantifiable results and hone their skills, but beware of doctors who transfer multiple embryos per transfer as this can result in better success rates (multiple births) at the expense of the health of both mother and babies
  • Facilities & technology – as a constantly evolving field, those clinics able to offer advanced procedures such as preimplantation genetic diagnosis (PGD), intracytoplasmic sperm injection (ICSI) and blastocyst transfers, can expect higher success rates
  • Patient cohort – success is largely determined by maternal age (IVF success rates decrease with age) and the underlying reason for infertility (genetic issues, lifestyle factors such as weight or smoking, quality of eggs and sperm). Some clinics may bolster their success rates by cherry picking younger women with less complex fertility issues and declining to treat more problematic cases. Conversely, a good clinic will be ready and willing to take on women with poorer prognoses and offer them tailor-made treatment that may not reflect well in their success rates

Regulators: The ART data collectors

In the United States, all IVF clinics must report their success rates to the Centers for Disease Control and Prevention (CDC). Additionally, many clinics are voluntary members of The Society for Assisted Reproductive Technology (SART), which also collects data including clinic success rates.

Since 1997, the European IVF Monitoring (EIM) Consortium of the European Society of Human Reproduction and Embryology (ESHRE) has collected data relating to ART from national registries (with either mandatory or voluntary participation) across Europe, as well as information reported by clinics themselves.

Go with your gut, not just your head

While nobody is disputing the importance of success rates, they are easily manipulated and should not be the deciding factor when choosing a clinic. The rapport you build with doctors and clinic staff, whether you are treated with compassion and respect; an individual and not just a statistic, is of vital importance. Patient testimonials, speaking to former patients and your own gut instinct will serve you well when making the right choice.

See our reviews on Google TrustPilot (an independent review site), or our own Patient Reviews. Also check out our YouTube Channel featuring numerous reviews.

Contributing writer: Natasha Robinson

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