Cumulative live birth rates after multiple IVF cycles

Researchers in a 2016 study compared cumulative live birth rates for double embryo transfers (day 3 fresh) for up to 8 cycles.

IVF success rates can be represented in different ways, although the number of live births per transfer, or per cycle, is most common. And when someone does one or two transfers, then this kind of success rate is often enough.

However, with frozen embryos and the ability to do multiple transfers from a single cycle (or having multiple IVF cycles), people want to know what their combined success rates are. This is sometimes called “cumulative” because we’re not just looking at one transfer, but all the transfers it takes to get pregnant or have a live birth.

It can be a bit confusing, so I think it helps to look at an example.

• 100 women have a single IVF cycle and they all have a fresh transfer.
• 25 have a live birth.
  • The live birth rate is 25%.
• The other 75 women have a second IVF cycle with a fresh transfer.
• 15 have a live birth.
  • So now the cumulative live birth = 25 (from the first transfer) + 15 (from the second transfer) = 40.
• So the cumulative live birth rate is 40/100 = 40%.

The key with cumulative rates is that we add up all the live births from successive IVF cycles. Then, when (and if) they get pregnant and have a live birth, this is noted as a cumulative live birth for that progression.

A 2016 study by McLernon et al. looked at cumulative live birth rates from nearly 180,000 women in the UK between 1992 and 2011.

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Results

For the cumulative live birth rates, they had two ways of presenting the data: “conservative” and “optimal”. These both had to do with handling women who discontinued treatment.

In the conservative estimate, they assumed these women didn’t have a live birth (because they couldn’t find out anyway), while in the optimal estimate, they assume that these women have the same chance of a live birth as the women who continued their treatment.

The real cumulative live birth rate likely lies somewhere in between these two estimates, so when I indicate these rates, I’ll be using the conservative estimate as the low end, and the optimal estimate for the high end. This is a bit different from how this study presents it, but I find it makes more sense this way. If you want more details on all of this I have some examples in the study details above.

Some caveats to keep in mind regarding this study:

• No indication of day 3 vs day 5 in the paper (although likely the majority were day 3)
• The majority of transfers were fresh
• Most transfers involved 2 embryos
• Most women completed all their IVF cycles within 2 years

For the cumulative live birth rates between 1999 – 2007:

• After 1 IVF cycle (107,347 women): 28.5%
• After 2 IVF cycles (46,439 women): 38.8% (conservative) to 45.6% (optimal)
• After 3 IVF cycles (17,913 women): 42.3% to 57.1%
• After 4 IVF cycles (6253 women): 43.5% to 65.3%
• After 5 IVF cycles (2175 women): 43.8% to 71.1%
• After 6 IVF cycles (793 women): 43.9% to 75.%
• After 7 IVF cycles (292 women): 43.9% to 79.2%
• After 8 IVF cycles (110 women): 44.0% to 82.4%

So, to be clear about this, after 8 IVF cycles the cumulative live birth rate is 44.0% to 82.4%. This means that all the women who had 8 IVF cycles had a 44.0% to 82.4% chance of a live birth at the end of it all.

The real value probably lies somewhere in between the 44.0% and 82.4%. It probably makes more sense to side towards the optimal estimates, because the women who drop out wouldn’t have a 0% chance of achieving a live birth. The problem is that they don’t know what the real rates are, so they have to present it both ways.

They also looked at age groups, but unfortunately this was only reported after 3 IVF cycles:

• For women <31: 52.4% (conservative) to 67.9% (optimal).
• For women 31-35: 50.3% to 64.2%
• For women 36-40: 33.9% to 47.0%
• For women >40: 9.8% to 17.3%

They also looked at the type of infertility (again, after the 3rd IVF cycle):

• For male factor: 45.8% (conservative) to 59.8% (optimal).
• For endometriosis: 44.8% to 57.5%
• For unexplained fertility: 42.2% to 56.2%
• Tubal infertility: 39.5% to 54.6%
• Anovulation: 39.4% to 57.6%
• Multiple diagnoses: 40.1% to 55.5%

Conclusions

Cumulative live birth rates in the UK from women using their own eggs increased after each successive IVF cycles, for both the conservative and optimal estimates. Based on age, the cumulative live births decreased beyond the age of 31. Based on infertility diagnosis, the rates didn’t change too much between different diagnoses.

The major issue with this study is that it’s dated and some data is missing.

This study also didn’t indicate day 3 vs day 5, though it was indicated that most transfers used two embryos. In 2011 approximately 75% of double embryo transfers were day 3 (Fertility Trends and Figures 2011 from HFEA) and overall 60-85% of transfers involved day 3 embryos. So it’s reasonable to assume that the majority of transfers were day 3 embryos.

Reference

McLernon DJ, Maheshwari A, Lee AJ, Bhattacharya S. Cumulative live birth rates after one or more complete cycles of IVF: a population-based study of linked cycle data from 178,898 women. Hum Reprod. 2016 Mar;31(3):572-81. doi: 10.1093/humrep/dev336. Epub 2016 Jan 18. PMID: 26783243.

 

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About Embryoman

Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.

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