Sources
Nothing on this site is written from memory. Each claim below names where it came from, so you can check it yourself or hand it to a clinician.
Why more than one organisation
Most of this site's HG facts come from the HER Foundation, and they are the best source alive on what this illness is actually like. But they are a patient-advocacy organisation, not a clinical guideline body, and a medical page resting on one source is one source away from being wrong. So the clinical claims here are checked against ACOG in the US, RCOG Green-top 69 in the UK, and the NHS. Where they disagree, this site says so rather than picking a favourite.
What HG is, and its complications
- HER Foundation, "More About HG": the definition of HG as a potentially life-threatening pregnancy disease, the morning-sickness comparison table (work, daily activities, energy, relationships, finances), the laboratory picture, the guidance to give IV nutrients such as thiamine with IV fluids, Wernicke's encephalopathy and its prognosis, and refeeding-syndrome risk. Read in a browser 2026-08-25. hyperemesis.org
- ACOG (American College of Obstetricians and Gynecologists), Morning Sickness: Nausea and Vomiting of Pregnancy: the US clinical position. Early treatment to prevent progression to HG, IV hydration with dextrose and vitamins where oral fluids are not tolerated, and thiamine before dextrose to prevent Wernicke encephalopathy. FAQ126, published May 2020, last reviewed November 2025. acog.org
- RCOG Green-top Guideline No. 69, the UK clinical guideline on nausea and vomiting of pregnancy and HG, covering community, day-care and inpatient management. It records that HG affects 0.3% to 3.6% of pregnancies, and that clinicians are advised against the term "morning sickness": it is inaccurate, and sufferers experience it as trivialising. rcog.org.uk
- NHS, Severe vomiting in pregnancy: the plainest public description of HG there is, and the UK route in. It puts HG at roughly 1 to 3 in every 100 pregnancies, notes cases go unreported, and says to contact a midwife, doctor or hospital as soon as food cannot be kept down. nhs.uk
- Pregnancy Sickness Support: ketones are not a reliable indicator of dehydration in this illness. pregnancysicknesssupport.org.uk
- StatPearls (NCBI Bookshelf), Hyperemesis Gravidarum: the clinical picture, including weight loss beyond roughly 5% of pre-pregnancy weight, dehydration and metabolic disturbance. ncbi.nlm.nih.gov
- HER Foundation, "Treatments": what the escalation words mean. Feeding tubes (NG and NJ), PICC lines and midlines, and TPN. Also that both PICC lines and midlines carry a clotting risk because pregnancy itself makes blood clot more easily, and that midlines carry less risk of complications from sepsis than PICC lines. Read 2026-09-04. hyperemesis.org
- American Dental Association, Oral Health Topics: Pregnancy: repeated vomiting erodes enamel, and brushing immediately afterwards makes the erosion worse. Rinse first, with water or a baking soda solution, and wait before brushing. Read 2026-09-04. ada.org
- Pregnancy Sickness Support, dental health and HG: the same guidance written for HG specifically, including the teaspoon of baking soda in a cup of water and the roughly one-hour wait before brushing. Read 2026-09-04. pregnancysicknesssupport.org.uk
Why it happens, and whether it happens again
The two recurrence figures on this site disagree with each other, and the site says so rather than choosing. Both are listed here so you can see who counted what.
- HER Foundation's summary of the 2023 Nature study: the cause is GDF15, not hCG as was long assumed. The placenta makes GDF15 in very large amounts in early pregnancy, and people genetically predisposed to HG carry variants leaving them with low GDF15 when not pregnant, which is what makes them hypersensitive to the surge. Read 2026-09-04. hyperemesis.org
- van der Minnen et al., American Journal of Obstetrics and Gynecology, May 2026 (PMID 41478545): a Danish population registry study of 1,447,968 pregnancies between 1998 and 2018. 1.9% had an HG diagnosis, with a recurrence rate of 26.0%. Those three figures are all this site takes from it. Abstract read 2026-09-04. pubmed.ncbi.nlm.nih.gov
- HER Foundation, "About Hyperemesis Gravidarum": recurrence as high as 80%, with HER's own studies consistently finding the recurrence risk exceeds 75%. HER also lists "you probably won't have it again" as a myth. Read 2026-09-04. hyperemesis.org
- Pregnancy Sickness Support, planning information: severe pregnancy sickness recurs in up to 80% of the same women, and there is good evidence that early, pre-emptive use of vitamin B6 plus a first-line medicine prevents the deterioration that leads to hospital admission. A 2013 randomised controlled trial found 2.5-fold fewer moderate-to-severe cases when treatment began before symptoms started. PSS publishes a preparation document for that conversation with a clinician. Read 2026-09-04. pregnancysicknesssupport.org.uk
Why being believed matters
- Policy-lab research on HG management (PMC): approximately 5% of women with HG terminate a wanted pregnancy and about 7% experience regular suicidal ideation, with difficulty accessing guideline-recommended care identified as a risk factor. ncbi.nlm.nih.gov/pmc
- Pregnancy Sickness Support, HG loss: around 50% of those suffering HG consider termination at some point, and around 10% of HG pregnancies end in termination. PSS lists the reasons people reach that point, states that "Termination feels like the last resort", treats it as a loss that needs grieving, and offers specialist HG counselling. Read 2026-09-04. pregnancysicknesssupport.org.uk
Support and referral
- HER Foundation: Get Help Now, the Family & Friends and crisis-support sections, the Professional Referral Network, the volunteer network, support groups, and the HELP Score. All links read off HER's own site in a browser 2026-08-25. hyperemesis.org/get-help-now
- HER Foundation, "Family & Friends" and "How to Help Her": the food-poisoning-for-months comparison; that she does not control her symptoms and cannot make them end sooner; that doing more usually makes her sicker; that a supporter's help is a major factor in the health of mother and baby; that the first three to four months are usually worst and HG typically eases by mid-pregnancy but may last until delivery; that HG was long misunderstood and some still wrongly assume it is psychological. The Crisis Warmline (+1 971-435-7444, callback usually within 24 hours) and the case-consultation donation figures come from the same pages. Read in a browser 2026-08-26. Family & Friends · How to Help Her
What this site will not do
It names no drug doses and recommends no treatment. Treatment for HG is individual and belongs to her clinicians. What this site gives you is the shape of the illness, the questions that get a real plan, and the words to use when nobody is listening.