Written by The HG Collective · Reviewed by HG Clinicians Expert Panel · Last reviewed: July 2026
How common is HG? UK statistics explained
Hyperemesis gravidarum (HG) affects a substantial number of pregnancies. If you are looking this up, you may be trying to understand what is happening to you or someone you care about. There is no single perfect figure because studies have defined, recognised and recorded HG in different ways.
Some studies count diagnosed HG or hospital admissions, while others combine HG with the wider category of nausea and vomiting in pregnancy. Those figures cannot be used interchangeably. This page focuses on HG and makes clear whenever a study uses a broader measure.
HG is not rare
The NHS says HG is thought to affect around 1 to 3 in every 100 pregnancies. RCOG's wider evidence range is 0.3% to 3.6%.
Those figures do not contradict one another. They reflect differences in how HG has been defined, recognised and recorded. The newer Windsor Definition should make future research more consistent, but older studies used several different diagnostic criteria.
Whichever estimate is used, HG is something maternity and primary-care services should expect to see regularly. It is not an obscure condition, and you should not have to prove that your illness is unusually rare before receiving care.
NHS patient guidance states that the exact number of pregnant women who develop HG is not known because some cases may go unreported, but estimates that it affects around 1 to 3 in every 100 pregnancies.[1]
RCOG's 2024 Green-top Guideline describes HG as affecting between 0.3% and 3.6% of pregnant women. It also recognises HG as the severe end of the nausea-and-vomiting-in-pregnancy spectrum, interfering with quality of life and the ability to eat and drink normally.[2]
The variation between estimates is partly explained by differences in study populations, case definitions and data sources. The internationally agreed Windsor Definition was introduced in 2021 to provide a consistent clinical and research definition for future studies.[3]
References
- [1] NHS. Severe vomiting in pregnancy. https://www.nhs.uk/pregnancy/complications/severe-vomiting/
- [2] Nelson-Piercy C, Dean C, Shehmar M, et al. The management of nausea and vomiting in pregnancy and hyperemesis gravidarum: Green-top Guideline No. 69. BJOG. 2024. https://doi.org/10.1111/1471-0528.17739
- [3] Jansen LAW, Koot MH, van't Hooft J, et al. The Windsor definition for hyperemesis gravidarum: a multistakeholder international consensus definition. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2021;266:15–22. https://doi.org/10.1016/j.ejogrb.2021.09.004
Does HG affect 30,000 pregnancies a year in the UK?
You may see the figure “around 30,000 a year” used in UK information about HG. It is important to understand what that number is: an estimate, not a national count of diagnosed cases.
The Office for National Statistics recorded 871,050 conceptions in England and Wales in 2023. Applying the NHS estimate of 1% to 3% to that figure gives approximately 8,700 to 26,100 pregnancies in England and Wales. The UK total would be higher once Scotland and Northern Ireland were included.
Even that calculation is incomplete. The ONS conception figures do not include pregnancies ending in miscarriage, and the HG percentage itself is an estimate. It is therefore reasonable to say that HG affects many thousands—and potentially tens of thousands—of UK pregnancies each year. It is not accurate to present 30,000 as though every case had been directly counted.
ONS recorded 871,050 conceptions among residents of England and Wales in 2023. In these statistics, a conception is a pregnancy ending in a maternity or legal abortion; pregnancies ending in miscarriage are not included.[1]
Applying the NHS estimate of 1% to 3% produces an illustrative range of approximately 8,700 to 26,100 affected pregnancies in England and Wales. This is a calculation, not an observed case count. It excludes Scotland, Northern Ireland and pregnancies ending in miscarriage, and it assumes the NHS percentage applies uniformly.[2]
Using RCOG's wider 0.3% to 3.6% range would produce a still wider estimate. This demonstrates why no single annual total should be presented as exact.[3]
References
- [1] Office for National Statistics. Conceptions in England and Wales: 2023. Released 26 June 2026. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/conceptionandfertilityrates/bulletins/conceptionstatistics/2023
- [2] NHS. Severe vomiting in pregnancy. https://www.nhs.uk/pregnancy/complications/severe-vomiting/
- [3] Nelson-Piercy C, Dean C, Shehmar M, et al. The management of nausea and vomiting in pregnancy and hyperemesis gravidarum: Green-top Guideline No. 69. BJOG. 2024. https://doi.org/10.1111/1471-0528.17739
How many people are admitted to hospital with HG?
The largest nationwide English hospital study examined more than 8.2 million pregnancies between 1997 and 2012. It found that 121,885 pregnancies involved at least one hospital admission for HG—around 1.5%, or approximately 1 in every 67 pregnancies in the study.
Repeat admission was common. Among pregnancies involving an HG admission:
- 72% involved one admission;
- 17% involved two admissions; and
- 11% involved three or more admissions.
That means 28% involved at least one readmission. If you have needed hospital treatment more than once, you are not an unusual case and you have not failed treatment.
These figures do not tell us how many people had HG altogether. They count hospital care in a historical English dataset and exclude people treated only by a GP, in ambulatory or day care, or not treated at all.
Fiaschi et al. analysed Hospital Episode Statistics for 8,215,538 pregnancies ending in live birth or stillbirth in England between 1997 and 2012. There were 186,800 HG admissions during 121,885 pregnancies, giving an admission prevalence of approximately 1.5%. Of the affected pregnancies, 72% involved one admission, 17% two admissions and 11% three or more.[1]
This study is large and nationally representative, but it measures hospital admission rather than every case of HG. It also uses historical data and excludes pregnancies not ending in a live birth or stillbirth.
A later English population study linked primary- and secondary-care records for 417,028 pregnancies. It found that relying on hospital admissions greatly underestimated the wider burden of clinically recorded nausea and vomiting in pregnancy and HG. The study combined NVP and HG in parts of its analysis, so its 9.1% overall figure must not be presented as an HG prevalence rate.[2]
References
- [1] Fiaschi L, Nelson-Piercy C, Tata LJ. Hospital admission for hyperemesis gravidarum: a nationwide study of occurrence, reoccurrence and risk factors among 8.2 million pregnancies. Human Reproduction. 2016;31(8):1675–1684. https://doi.org/10.1093/humrep/dew128
- [2] Fiaschi L, Nelson-Piercy C, Deb S, King R, Tata LJ. Clinical management of nausea and vomiting in pregnancy and hyperemesis gravidarum across primary and secondary care: a population-based study. BJOG. 2019;126(10):1201–1211. https://doi.org/10.1111/1471-0528.15662
The mental health impact is common and serious
HG is a physical illness, but living with relentless nausea, vomiting, isolation, loss of independence and difficulty obtaining effective care can have a profound psychological effect.
In a prospective UK study of women receiving hospital treatment for HG, 49% met the screening threshold for probable antenatal depression, compared with 6% of women without HG. Six weeks after birth, 29% met the threshold for probable postnatal depression, compared with 7% of controls.
A separate online UK survey of more than 5,000 people with self-reported HG found that 25.5% reported occasional suicidal thoughts and 6.6% reported regular suicidal thoughts because of the severity of their sickness. Together, that was 32.1% of survey respondents.
This does not mean that one in three people with HG across the whole population will experience suicidal thoughts. The survey was self-selected and cannot establish a population prevalence rate. It does show that suicidal thoughts were reported by a substantial number of people living with severe HG and must be taken seriously.
If HG is affecting your mental health, tell your GP, midwife or maternity team. If you feel unable to keep yourself safe or think you may act on suicidal thoughts, call 999 or go to A&E now.
Mitchell-Jones et al. conducted a prospective case–control study across three London hospitals, recruiting 106 women admitted with HG and 108 controls. Probable depression was measured using a validated screening questionnaire; it was not a confirmed clinical diagnosis. Probable antenatal depression was identified in 49% of the HG group and 6% of controls. At six weeks after birth, the figures were 29% and 7% respectively.[1]
Nana et al. used an anonymous online survey completed by more than 5,000 respondents with self-reported HG. Occasional suicidal ideation related to severe sickness was reported by 25.5% and regular suicidal ideation by 6.6%. Greater sickness severity, poorer functioning and poorer perceived quality of care were associated with suicidal ideation. Because recruitment was online and self-selected, these percentages describe the survey respondents and should not be generalised as a population prevalence estimate.[2]
A 2026 mixed-methods systematic review brought together 64 international studies of HG and nausea and vomiting in pregnancy. Depression and anxiety were generally higher in people with HG than in controls, with additional evidence of psychological distress, trauma-related symptoms, suicidal ideation and poorer mental-health-related quality of life. The review concluded that psychological morbidity was associated with both symptom severity and experiences of care.[3]
References
- [1] Mitchell-Jones N, Lawson K, Bobdiwala S, et al. Association between hyperemesis gravidarum and psychological symptoms, psychosocial outcomes and infant bonding: a two-point prospective case–control multicentre survey study in an inner city setting. BMJ Open. 2020;10:e039715. https://doi.org/10.1136/bmjopen-2020-039715
- [2] Nana M, Tydeman F, Bevan G, et al. Hyperemesis gravidarum is associated with increased rates of termination of pregnancy and suicidal ideation: results from a survey completed by >5000 participants. American Journal of Obstetrics and Gynecology. 2021;224(6):629–631. https://doi.org/10.1016/j.ajog.2021.03.006
- [3] Mills A, Glaister P, Heys S, Hibberd C, Coxon K. Experiences of psychological burden and care in women with hyperemesis gravidarum and nausea and vomiting in pregnancy: a mixed-methods systematic review. Midwifery. 2026:104956. https://doi.org/10.1016/j.midw.2026.104956
A gap in early identification
HG begins early in pregnancy, but routine identification is not yet built consistently into maternity care.
A national service evaluation contacted all 139 maternity units in England, Scotland and Wales and received responses from 129. Only 37 units—28.7%—reported routinely screening for nausea and vomiting in pregnancy or HG at the booking appointment. Routine mental health screening for people with NVP or HG was reported by 54 units, or 41.9%.
NICE recommends that the first antenatal booking appointment takes place by 10 weeks and includes assessment of the woman's health and individual care needs. However, NG201 does not specifically recommend routine screening for NVP or HG at booking. The low screening rate therefore represents an opportunity to improve early identification, rather than evidence that maternity units are failing to follow a specific NICE screening requirement.
Nana et al.'s national service evaluation approached all 139 maternity units in England, Scotland and Wales and received 129 responses, a response rate of 92.8%. Routine NVP/HG screening at booking was reported by 37 of 129 units (28.7%), while routine mental health screening was reported by 54 of 129 units (41.9%).[1]
NICE recommends a first antenatal booking appointment by 10+0 weeks and says that the woman's medical history, general health, wellbeing and individual care needs should be considered. NG201 also contains recommendations for managing nausea and vomiting once it is identified. It does not, however, specifically require maternity services to screen every woman for NVP or HG at booking.[2]
References
- [1] Nana M, Suff N, Gregori M, et al. How are hospitals in England, Scotland and Wales caring for women with nausea and vomiting in pregnancy: a national service evaluation. BMC Health Services Research. 2025;25:1128. https://doi.org/10.1186/s12913-025-12909-0
- [2] National Institute for Health and Care Excellence. Antenatal care. NICE guideline NG201, recommendations 1.1.1–1.1.4. Updated 2025. https://www.nice.org.uk/guidance/ng201/chapter/recommendations