Overall success rate in the treatment clinic
The HFEA 2002 report has demonstrated that in the UK, the overall live birth rates per IVF treatment cycle was 22% and varies between different clinics. It ranged from anywhere between 10% to 46%.
What are the possible causes for the difference in IVF success rates?
The size of the clinic
In general, large IVF centres have higher success rates than small clinics. However, some small clinics have very good results.
Live birth rate per treatment cycle
| UK | USA | |
| Information source | HFEA 1997 Report | SART 2002 Report |
| Large centres | 15.7% | 34.3% |
| Small centres | 12.6% | 30.0% |
Skill and experience of the team including, doctors, nurses and embryologists
Even in the same clinic with the same clinical protocol and a single embryology laboratory, IVF outcome varies between different doctors. Karandi et al 1999 (Fertility & Sterility Journal) reported that the clinical pregnancy rates vary between 8.3 to 40% between different physicians. Similarly IVF outcome varies between different embryologists (source Fertility & Sterility Journal 1999).
The technique of embryo transfer
Variations in embryo transfer techniques can affect the result of the treatment.
The type of ovarian stimulation protocol
Natural cycle or clomiphene stimulated IVF have poor success rates per treatment cycle compared to Gonadotropin-releasing hormone (GnRh) agonists and gonadotropins.
GnRh agonists in addition to gonadotropins for ovarian stimulation result in higher pregnancy and live birth rates than using gonadotropins alone.
There is a small but significant increase in pregnancy rates following the use of high purity gonadotropins or recombinant FSH compared to hMG.
Quality of cycle monitoring
Assisted hatching and blastocyst transfer
There is some evidence that assisted hatching in selected groups of patients, result in improvement of pregnancy and live birth rates. Similarly, there is evidence that blastocyst transfer result in improvement in pregnancy and live birth rates with lower incidence of multiple pregnancy rates because of transfer of less number of embryos.
| Age group | less than 35 | 35-37 | 38-40 | 41-42 | 43 or over |
| Blastocyst transfer | 44.3% | 37.6% | 29.4% | 18% | 7.5% |
| Cleaved embryo transfer | 37.6% | 32.7% | 24.4% | 14.3% | 5.7% |
Live birth rate per treatment cycle using donated own eggs. Data adapted from SART report 2000