Research highlights

• New insight on which treatments are most effective.
• Improved understanding of risk of multi-embryo transfers.
• More cycles funded by the NHS.

One in six couples have difficulty conceiving. In vitro fertilisation (IVF) is now a routine treatment that offers hope – but it is time consuming, expensive, emotionally demanding for couples and can lead to complications related to multiple pregnancies and preterm births.  

Research by a team at Bristol team has provided greater clarity for couples and clinicians by confirming which IVF treatments work best and reduce risk of harm for the baby.

The findings have also influenced changes to clinical practice and IVF funding in the UK – providing a significant boost for couples that rely on publicly-funded treatment.  

Unprecedented research 

The team led by Professor Deborah Lawlor addressed shortfalls in understanding of the impact of different IVF practices by analysing a UK-wide dataset of all IVF cycles since 2003.  

Using data on over 100,000 cycles, they produced new evidence that single embryo transfer should be the routine approach in women under 40 and a double embryo transfer the norm in those over 40, with triple transfers phased out.

Combined, this approach delivers equivalent or higher live-birth rates but with a lower risk of harm from multiple births, preterm births and babies born small for their gestational age.  

The team also provided new insight for healthcare providers who make decisions on how many cycles it is cost effective to fund.

Research in this area indicated that the cumulative live-birth rate in all women continued to increase up to nine IVF cycles, and that in women under 40 couples could achieve a rate similar to that of couples conceiving naturally with six cycles.  

The team also identified how key characteristics (such as a woman’s age) and related treatments interact with each other. For example, they provided evidence that more live-births happen with donor eggs at all ages, but are strongest at older ages.

They also showed that intracytoplasmic sperm injection (ICSI) increases live-birth rates in those with male-related infertility. Together, these findings enabled the team to produce a model for predicting positive IVF outcomes that was far more accurate than any previous model.   

Influence on IVF practice and policy 

The research has had a profound impact on both IVF practice and policy. In the UK, The Human Fertilisation and Embryology Authority (HFEA) used the findings to promote single embryo transfers in younger women and double transfer in older women – leading to significant reductions in multiple pregnancies and births.

Single embryo transfers alone increased 45% to 60% from 2013 to 2016. The Chief Executive of HFEA described the importance of the research in ‘providing continued momentum for our campaign to promote ‘one at a time’ embryo transfers and see IVF related multiple births, with their associated risk of preterm birth and low birth weight, reduced.’  

The research was cited in a Scottish National Infertility Group government report that resulted in Scotland changing its guidelines to fund up to three full cycles on the NHS from 2017 (up from a previous limit of two).

The proportion of all IVF cycles publicly funded in Scotland has since increased from 56% to 62% - improving access for those that can’t afford private treatment.  

In England, the National Institute for Health and Care Excellence (NICE) has created similar guidance that up to three cycles of IVF should be offered on the NHS.  

Although some of the regional Integrated Care Boards (ICBs) still only offer one cycle, hope remains that that the continued existence of the NICE guidance, along with pressure from other groups such as the HFEA, the Royal College of Obstetrics and Gynaecology and patient groups - all of which have drawn heavily in the Bristol research to support recommendations - will lead to more ICBs offering three cycles in the future.