1. Methodology background
Submitted by all HFEA licensed fertility clinics
United Kingdom (UK)
Approximately 86,000 cycles per annum
Document last revised
27 May 2021
2. About this quality and methodology report
This quality and methodology document contains information on the quality characteristics of the data (including the European Statistical Services five dimensions of quality) as well as the methods used to create it. The information in this document will help you to:
understand the strengths and limitations of the data
learn about existing uses and users of the data
reduce the risk of misusing data
help you to decide suitable uses for the data
understand the methods used to create the data.
3. Important points
3.1. All licensed fertility clinics in the UK are required by law to provide information to the HFEA about treatments they carry out and their outcomes. We hold this information on our Register, which contains information about fertility patients, partners, donors, treatments and children born as a result of these treatments.
3.2. The information that we publish is a snapshot of Register data as at 12/12/2020. Results are published according to the year in which the cycle was started.
3.3. By this date, clinics were required to have submitted all records of 2019 births. At the time of running this report, however, there were circa 2,300 outcomes not yet reported.
3.4. As our database consists of a live Register and we rely on accurate reporting from clinics, information may be subject to change and the figures published here may differ slightly to those published before or in the future.
3.5. This publication reports national data trends over time. Clinic-specific data is published on our website’s clinic search tool, Choose a Fertility Clinic.
4. Quality summary
We make information from the Register available to patients, clinic staff, media, researchers and the public to show how fertility treatment has changed over time. We publish annually data from our Register on treatment and outcomes, covering treatment type, age group, partner type, ethnicity, donor information, funding status, English region and UK nations. The data published is a snapshot of our Register data submitted by clinics and is subject to change.
5. Quality characteristics of Fertility Trends, UK Register data
The Human Fertilisation and Embryology Act 1990 made it a legal requirement for every licensed fertility clinic in the UK to submit information on all fertility treatments and children born as a result to the HFEA. The HFEA holds a Register of these treatments since 1991, which is believed to be the largest database of fertility treatment in the world. We produce this statistical release on an annual basis with an underlying dataset. We do not hold detailed information on partner intrauterine insemination (IUI) or surrogacy that takes place outside of licensed clinics, which are not regulated by the HFEA.
5.2. Accuracy and reliability
We report on cycle level information rather than patient level information. We make an estimate of the number of patients but owing to multiple and sometimes inconsistent registrations at different clinics, cycles are the default reporting method.
For a typical cycle, clinics will initially report patient registration, cycle-related information and early outcomes (including pregnancies) in line with General Direction 0005. Clinics then have 12 months to subsequently report the outcome of cycles for which they reported a pregnancy.
The Register undergoes regular validation – this was last completed in December 2020. Treatment cycles performed on or before 31 December 2019 have been verified along with their pregnancy status. Live births have been verified for treatments that took place on or before 31 December 2018. One centre has been removed from the analysis due to data quality issues. Another centre, also experiencing data issues, has been included due to the negative impact of exclusion on data analysis. We estimate that this centre will have around 600 cycles and 200-250 live births missing and therefore under-reported in the analysis.
An additional four centres were unable to complete the data verification process to the required deadline. These centres have been included, but the data supplied may include some minor inaccuracies.
We have calculated preliminary birth rates for 2019 as outlined in section 6.2. Based on previous validation, we expect these rates are accurate to approximately 1.5 percentage points. We have excluded 1,540 cycles (over 2017-2019) due to technical issues at one centre that resulted in reporting errors.
Ethnicity was the variable with the largest proportion of missing values - 10% of cycles in 2019 had no ethnicity recorded.
5.3. Coherence and comparability
Although there is no standard definition of an IVF cycle, the HFEA counts a cycle as an embryo transfer, or equivalent stage if no embryos are created. Any remaining frozen embryos used subsequently are counted as new cycles. This may differ from a clinical commissioning group’s definition of a cycle.
We recommend that readers always view the latest version of Fertility Trends, which includes data going back to 1991. This is because inclusions and exclusions may change year on year as we improve our methodology. For example, pre-2018 we did not have the same exclusions on birth rates that we do now, and in 2019 we took the decision to exclude under 18’s and over 50’s when showing age-related data. Any exclusions or inclusions are applied not just to the latest year, but to all previous years, ensuring comparability.
Licensed clinics have been required to provide Register information to the HFEA since 1 August 1991. Clinics report data based on our collection forms and the information requirements have changed over time. The Human Fertilisation and Embryology Act 2008 contained provisions enabling two females in a same-sex couple to register a birth from 1 September 2009 onwards. Where possible, historical data is provided for comparison. HFEA data is presented by the year in which the treatment cycle started, not the year in which a resulting birth was reported. Other data providers, such as the Office for National Statistics (ONS), publish birth rates according to the year the child was born. There are different ways to account for the outcomes of treatment. Our live birth data counts all births where one or more babies were born showing some sign of life, including those who sadly go on to die within the first month of life (neonatal deaths).
Our multiple birth data counts only births where two or more babies were born alive, including those where one or more of the babies died within the first month of life. Still births – where a baby is born after 24 weeks gestation showing no signs of life – are not included in either live birth or multiple birth counts in the period covered by the reports due to the way clinic birth rates are currently reported. This means that a multiple pregnancy which results in the birth of one live baby and one stillborn baby is not counted within our data as a multiple birth. The ONS however, classes a multiple birth as a pregnancy resulting in the birth of more than one baby, whether alive or stillborn.
Clinical improvements have led to increased chances of a live birth for most patients since 1991 as freezing techniques have improved with the introduction of vitrification in lieu of slow freezing.
There is a large degree of comparability in birth statistics between countries within the UK; the regions included in the reports are based on the location of the clinic rather than patient’s residency. Internationally, we provide data to ESHRE each year to allow publication of UK fertility treatment and outcome figures alongside those of other European countries.
Fertility Trends is our annual publication on national and regional trends in fertility treatments and live birth rates. Clinic-level information is published on the HFEA Choose a Fertility Clinic, website and may differ due to different reporting periods and processes.
5.4. Accessibility and clarity
Our recommended format for accessible content is a combination of HTML web pages for narrative, charts and graphs (including alt-text), with data being provided in usable formats such as Excel spreadsheets. We published our annual report in HTML format for the first time in 2020, and all future reports will take this format. Underlying datasets provide more detailed statistics. Our website also offers users the option to download the narrative in PDF format. Alternative formats can also be requested for all tables/figures in our reports.
5.5. Timeliness and punctuality
A snapshot of Register data is extracted each year and we aim to publish this data in Fertility Trends in May of each year. There is a two-year time lag in the data on which we report e.g. in 2021, we report on treatments that took place in 2019, allowing 12 months for birth outcomes to occur and to be reported by clinics to the HFEA.
6. Concepts and definitions
6.1. Cycles and treatment cycles
The term ‘cycle’ covers the range of reasons patients undergo fertility treatment: with the intention of becoming pregnant as soon as possible (most patients), fertility preservation (a small but growing number of patients), or with the intention of donating eggs or embryos.
The term ‘treatment cycle’ or ‘treatment now’ includes only those cycles where the patient recorded on their registration form that they intended to try to become pregnant as part of their treatment (IVF, DI and egg sharing cycles are always treatment cycles).
This distinction is important because it has an impact on the birth rates we report. Throughout the reports, we use ‘treatment cycles’ to assess outcomes. Birth rates are calculated for those patients that intended to become pregnant to avoid underestimating the live birth rate.
6.2. Success rates
The calculation of success rate includes only cycles intended for treatment now and only cycles where the relating outcome is recorded on the Register. Pre-implantation genetic diagnosis (PGT-M) and Pre-implantation genetic testing for aneuploidy (PGT-A), which involves checking the chromosomes of embryos prior to treatment, have been excluded.
To give patients a clear idea of their own chance of success, we present overall live birth and pregnancy rates with patient eggs only, excluding donor eggs and surrogacy to mitigate for the fact that donor eggs are likely to be frozen at a younger age and may artificially inflate the chances of a live birth rates. Fresh and frozen cycles have been presented separately where possible. Pregnancies are counted as any cycle where foetal heart pulsations are seen.
We use per embryo transferred to measure IVF success rates as we believe it is the most appropriate measure of a clinic’s practices and success. The data for DI and IVF birth rates per treatment cycle are available in the underlying data tables for completeness.
All the success rates we quote in these reports are for one full calendar year. They are calculated as follows:
- Birth/pregnancy rate per embryo transferred: the number of live birth/pregnancy occurrences divided by the sum of embryos transferred in that year
- Birth/pregnancy rate per treatment cycle: the number of live birth/pregnancy occurrences divided by the number of treatment cycles started
6.3. Multiple pregnancy and birth rates
The calculation of multiple birth rate includes only cycles intended for treatment now and only cycles where relating outcome is recorded on the Register. In contrast to success rates, it includes PGT-M, PGT-A, surrogacy cycles and all egg sources.
- Multiple pregnancy rate: the total number of multiple pregnancies divided by the total number of pregnancies
- Multiple birth rate: the total number of multiple births divided by the total number of live birth occurrences
6.4. Adverse outcomes
Multiple adverse outcomes can be reported in a single cycle – each of these outcomes is reported individually in the tables provided. For example, if an early outcome form states miscarriage and ectopic, it will be counted twice in the table – once in miscarriages and once in ectopic.
7. Methods used to produce reports using UK Register data
The figures supplied in these reports are from our data warehouse containing Register data as at 12/12/2020. A snapshot of data is pulled using Microsoft SQL and fed into Tableau where data analysis and visualisation can take place.
The information that we publish is a snapshot of data provided to us by licensed clinics at a particular time. Guidance note 32 in the HFEA Code of Practice sets out the legal basis and requirements which govern our interaction with licensed clinics and third-party providers. We work closely with clinics and third-party systems to ensure the importance and guidance around submission of Register data is understood through stakeholder groups, workshops and sharing good practice.
We use additional quality assurance processes, including: manually validating data submissions; carrying out regular quality assurance checks on data through the inspection process; publishing non-compliances with data quality issues in inspection reports; where relevant, reviewing quality reports and targeting clinics for audit where irregular data has been submitted. In publication we suppress values under five and any calculations with numerators and denominators below five are also supressed.
Review date: 8 February 2024