1. Methodology background
|Submitted by all HFEA licensed fertility clinics
|United Kingdom (UK)
|Approximately 86,000 cycles per annum
|Document last revised
|30 November 2022
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, treatment and children born as a result of these treatments.
3.2. The information that we publish is a snapshot of Register data as at 28/08/2021. Results are published according to the year in which the cycle was started, unless explicitly stated otherwise.
3.3. By this date, clinics were required to have submitted all records of 2020 outcomes including births; however, due to the pressures of COVID-19 on clinics and a large-scale data migration project for our data register, outcomes from 2020 remain unvalidated. As we are unable to provide estimations on missing outcomes due to uncertainties from COVID-19, outcomes for 2020 will not be provided until 2023 when data validation is due to be completed.
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, as well as in our State of the Sector reports.
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 statistical releases 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 is 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 missing and therefore under-reported in the analysis. Additionally, data on Northern Ireland is excluded throughout the Impact of COVID-19 on fertility treatment 2020 report when comparing information by nation, this is due to one clinic accounting for 83% of annual cycles in Northern Ireland experiencing data reporting errors. Results are published according to the year in which the cycle was started.
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.
Surrogacy cycles have been excluded from calculations relating to egg, sperm and embryo donation cycles due to the difficulty in determining whether donations were provided by intended parents on our data register.
We have not included outcome information from treatments began in 2020 in these reports due to the length of time since our last validation was performed (December 2020) and the uncertainties presented with COVID-19 changes as outlined in the Impact of COVID-19 on fertility treatment 2020 report. We have excluded 2,400 cycles (over 2017-June 2021) 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.
In the Trends in egg, sperm and embryo donation 2020 report, the indicator of whether an individual has their own child was the variable with the largest proportion of missing values. The number of boys and girls an individual has was used to provide data in some instances where this information was missing. For 18% of new egg donors and 16% of new sperm donors registering in 2010, their own child status was not recorded. We note that these figures were lower in other years with 5% and 4% respectively in 2020.
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 our 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. Due to uncertainties in estimations in data variation due to changes from the COVID-19 pandemic and a large-scale data migration project moving our 30-year fertility register to a new system, the latest available Fertility trends report is Fertility trends 2019. We are currently upgrading our systems to enable us to better use our data for patients, clinicians and researchers and expect this work to be completed by winter 2022/23. 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. Alternative formats can 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 Impact of COVID-19 on fertility treatment 2020 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
We note that in the Trends in egg, sperm and embryo donation 2020 report, success rates comparing patients using their own eggs and donor eggs are given. For these calculations, patients using donor eggs, donor embryos and both donor eggs and donor sperm are combined. Success rates may differ between these three categories.
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 births
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.
6.5. Donor registrations
In previous publications, the HFEA has provided the total numbers of donor registrations, including donors re-registering. In the Trends in egg, sperm and embryo donation 2020 report, only a donor’s first registration has been included. This has been done to prevent donors who are registered multiple times being overrepresented.
6.6. Donor countries
Various form changes mean that the country a donor made their donation in has not always been recorded. Where such is the case, we have looked at whether a donor’s postcode has the UK format to determine whether they resided in the UK.
We note that not all donors imported from a particular country will be residents of that country. However, this is not believed to be the case for the majority of donors.
6.7. Index of multiple deprivation
Indices of multiple deprivation were calculated in England using 2015 data from the Department for Levelling Up, Housing and Communities. The 2015 edition of this dataset was chosen, as this data was being linked with donor registrations from 2011-2020, and 2015 is approximately the midpoint of this period.
The HFEA records donor postcodes, and these were linked with the above data using data from the Office for National Statistics. In a small number of cases, postcodes may not have been provided in an accessible format, and as such were excluded from this data.
We are unable to comment on these trends for Northern Ireland, Scotland and Wales with any certainty due to small numbers.
When the requirements for sperm and egg donors to be identifiable were introduced, a transition period was allowed for. In specific circumstances in the first year (where the patient had already had a child using a particular donor, for example), sperm and eggs from donors who donated anonymously could be used. For the purposes of these statistics, the following approximation has been used:
- If the donor has submitted a form to the HFEA indicating they wish to be identifiable to their genetic children, they were considered identifiable.
- If a treatment took place after 31 March 2006 and used a donor, then that donor was considered identifiable.
- If a treatment took place after 31 March 2005 and before 1 April 2006 and used a donor who donated after 31 March 2005, then the donor was considered identifiable.
- If a treatment took place after 31 March 2005 and before 1 April 2006, used a donor who donated prior to 31 March 2005 and the patient had not undergone IVF or DI previously using that particular donor, then the donor was considered identifiable.
However, we should emphasise that this is an approximation. When an individual applies for information from the HFEA on their donor, their child’s donor, or their donor-conceived children, a more individualised approach is taken to determine what information may be released.
6.9. Reciprocal IVF
Reciprocal IVF, or shared motherhood, is a procedure used by female same-sex couples, in which one partner has their eggs collected and used to create an embryo, and then the other partner has the embryo transferred and carries the pregnancy. The HFEA does not collect data on where this has happened, and so it has been approximated as when the date of birth of the egg donor and partner match, and when at least one of the following is satisfied:
- The egg donor’s surname and the partner’s surname match
- The egg donor’s surname at birth and the partner’s surname match
- The egg donor’s surname and the partner’s surname at birth match
- The egg donor’s surname at birth and the partner’s surname at birth match
Due to the way the data is stored on the register, for instance not having an identifier for reciprocal IVF cycles recorded, this data has previously been provided in data reports within egg donation cycles. The approximation detailed above has been used to ensure this is excluded in the Trends in egg, sperm and embryo donation 2020 report as the intention is not for the eggs collected to be used in donation.
6.10. Donors living with a partner
We collect information on whether egg or sperm donors were Single, Divorced, Widowed, in a Civil Partnership, Married, or Cohabitating on donor registration forms. This information has been used to approximate how many egg or sperm donors were living with a partner at the time of their registration. The “Not living with a partner” category includes egg and sperm donors that registered as Single, Divorced or Widowed. The “Living with a partner” category includes egg and sperm donors that registered as in a Civil Partnership, Married or Cohabitating. We recognise that these groupings will not be perfectly accurate, as an individual could for instance be married to someone and not living with them. These numbers are intended as an estimate.
6.11. Donors own children
At registration, egg and sperm donors can indicate whether they had their own children, as well as the number of children they have by sex. For the Trends in egg, sperm and embryo donation 2020 report, a donor has been taken as having a child if they either indicated on their registration form that they had their own child or if they indicated that they had at least one boy/girl, egg and sperm donors were taken as having no children if it was indicated on the registration form that they either had no children or if they indicated that they had no boys/girls.
6.12. Distinction between donor embryos and separately donated sperm and eggs
Due to the way data is collected in clinics, we cannot easily distinguish between a patient using a donated embryo, and a patient using separately donated sperm and eggs in their treatment. As such, these have been combined in previous HFEA publications. This distinction is discussed in the Trends in egg, sperm and embryo report, for which treatments using explicitly donated embryos were identified by:
- The sperm and eggs both being sourced from donors.
- The egg donor’s date of birth and surname matching with the date of birth and either current or birth surname of a patient who has donated embryos.
- The sperm donor’s date of birth and surname matching with the date of birth and either current or birth surname of the partner of the patient in the above.
- The treatment not being for surrogacy.
We emphasise that this is a minimum estimate from our records, and the true values may differ.
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: 16 February 2025