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What’s the difference between cumulative success rates and success rates per embryo transfer?

Understanding IVF statistics helps making the best decision for the future.

Deciding and choosing fertility treatments, we have many factors to compare. Starting from very practical and easy to grasp and ending with those more difficult to understand, such as success rates. How are they measured? What are the differences in presenting data by clinics? How to read the rates to decide right?

In 3on1 #IVFANSWERS the experts explain how to understand success rates which is the most crucial statistic in fertility treatment:

  • Dr Àlex García-Faura Scientific Director of Institut Marquès Ireland
  • Dr Diana Obidnyak – Head of International Cooperation Department AVA Peter Clinic
  • Dr. Miguel Ángel Checa – Specialist in Obstetrics/ Gynecology and Reproductive Medicine / Fertty International
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Dr Diana Obidnyak, AVA Peter Clinic, Russia

Answer from Dr Obidnyak - Specialist in Obstetrics

What does cumulative pregnancy rate mean? Actually around 30% of patient burnout after unsuccessful IVF is mainly associated with emotional and physical burn-out, the poor chances of success after continued treatment and financial expenses. With the aim to facilitate the assessment of chances of successful outcome, the term ‘the cumulative live birth rate’ has been implemented. The term ‘cumulative’ is derived from the Latin word ‘cumulare’ (‘to accumulate’).
According to the actual definition, the cumulative pregnancy rate takes account of all pregnancies achieved by successive several embryo transfers, irrespective of whether these embryos derived from the so-called fresh cycles or frozen thawed embryo transfers. Interestingly, the cumulative pregnancy rate also implies that the chances of getting pregnant increase with the number of received therapy cycles. The decision whether a woman should start a continued IVF treatment should belong to both a fertility specialist and a patient who are assessing all medical and non-medical issues.

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Dr. Miguel Ángel Checa, Fertty International, Spain

Answer from Dr Checa - Specialist in Obstetrics/ Gynecology

The most crucial change in the assisted reproduction in last years has been a vitrification.
Nowadays we have the same chance of pregnancy when transferring fresh embryos or frozen embryos. This change has made us to change the nomenclature of the pregnancy chances. A few years ago we talked about a pregnancy chance when we transferred one fresh embryo. Nowadays we talk about a cumulative pregnancy chance when we count all the transferred embryos: both fresh and frozen.

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Dr Àlex García-Faura, Institut Marquès, Spain

Answer from Dr García-Faura Scientific Director

When we talk about success rates in fertility treatments, we need to make sure that we know exactly what we are talking about. Patients would use success rates to compare fertility treatments and fertility clinics before making a decision on where to undergo their own fertility treatment. Of course the goal of any fertility treatment is having a healthy baby at home so the most important success rate would be simply a healthy baby at home or the newborn rate. But of course from a medical point of view, we will use other success rates to compare the results of different fertility treatments. We have a pregnancy rate which is having a positive pregnancy test. We also have a viable pregnancy rate which means having a normal pregnancy which would exclude ectopic pregnancies and miscarriages. So when we are looking at success rates per treatment, we need to make sure if we are talking about a baby at home, a viable pregnancy or a positive pregnancy test. When also need to make sure if we are talking about success rates per transfer or per started treatments. During treatment, we might need to cancel the cycle for different reasons, such as no follicle growing under ovarian stimulation, no oocytes after pick up or no mature oocytes.
Sometimes fertilisation will fail and we won’t have any embryos. And even if we have day 5 embryos, sometimes the cycle has to be cancelled because they’re not high quality blastocysts or they’re abnormal from a chromosomal point of view. So it is very important if we are talking about success rates per transfer – when a patient finally has a high quality blastocyst to transfer – or success rates every time we start a treatment.
Finally, we need to explain the difference between a pregnancy rate per transfer and a cumulative pregnancy rate. The pregnancy rate per transfer is the chance of having a positive pregnancy test after a single transfer. The cumulative pregnancy rate refers to the results after the transfer of all the embryos that we had from one ovarian stimulation. It may include fresh embryo transfer and sometimes also thawed embryo transfer from the same ovarian stimulation. If after the transfer of a high quality day 5 embryo, we have a pregnancy rate up to 65 % and still one frozen embryo to transfer, the cumulative pregnancy rate may rise up to 85-86%. And if afterwards we still have a third embryo to transfer, this pregnancy rate might be over 90%. So when we compare results, we need to make sure if we are talking about pregnancy rates per transfer or cumulative rates for the whole cycle of fertility treatment.

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3on1 IVFanswers - three answers to one question

Three IVF experts answering the same question.

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