The Management of Nausea and Vomiting in Pregnancy and Hyperemesis Gravidarum (Green-top Guideline No. 69)

Use an objective, validated index like the Pregnancy-Unique Quantification of Emesis (PUQE) or HyperEmesis Level Prediction (HELP) tools to classify the severity of NVP and HG.

Ketonuria is not an indicator of dehydration and should not be used to assess the severity of NVP or HG.

Prescribe first-line antiemetics when required for NVP and HG, for which there are good safety and efficacy data, such as anti(H1)histamines, phenothiazines, and doxylamine/pyridoxine (Xonvea®).

Ondansetron is a safe and effective second-line antiemetic; its use should not be discouraged if first-line treatments fail.

Metoclopramide is a safe and effective antiemetic that can be used as a second-line therapy, alone or in combination with other agents.

Use combinations of different antiemetic drugs in women who do not respond to a single agent.

The most appropriate intravenous hydration is normal saline (0.9% NaCl) with added potassium chloride in each bag, with the administration rate guided by daily monitoring of electrolytes.

Give thiamine supplementation to all women admitted with vomiting or severely reduced dietary intake, especially before administering dextrose or parenteral nutrition.

Offer thromboprophylaxis with low-molecular-weight heparin (LMWH) to women admitted with HG.

Ask about previous adverse reactions to antiemetic therapies and promptly stop any medication that causes an adverse reaction.

Consider termination of pregnancy only after all other therapeutic measures have been tried and documented.

Nausea and Vomiting of Pregnancy (NVP) affects up to 90% of pregnant women. The term 'morning sickness' is inaccurate as symptoms can occur throughout the day.

Hyperemesis Gravidarum (HG) is a severe form of NVP affecting 0.3–3.6% of pregnant women, interfering with quality of life and normal eating/drinking. Recurrence rates range from 15% to 89%.

The major mechanism of NVP and HG is now understood to be hypersensitivity to the hormone growth differentiation factor-15 (GDF15).

NVP is diagnosed when symptom onset is prior to 16 weeks of gestation and other causes of nausea and vomiting have been excluded. If onset is after 16 weeks, investigate other causes.

HG can be diagnosed based on the Windsor definition (patient-focused criteria):

The typical course of NVP starts between 4-7 weeks, peaks around 9 weeks, and resolves by 20 weeks in 90% of women.

Use objective, validated indices to classify severity and monitor treatment response:

Ketonuria is not an indicator of dehydration in pregnancy and should not be used to assess the severity of NVP or HG. Its use may mislead clinical judgement.

Common investigation findings in severe NVP/HG include:

Community Care: For women with mild NVP who are not dehydrated. Management includes oral antiemetics, reassurance, oral hydration, and dietary advice (eat little and often).

Ambulatory Day Care: For when community measures fail (e.g., unable to tolerate oral antiemetics or fluids). Provides intravenous fluids, vitamins (especially thiamine), and parenteral antiemetics.

Inpatient Care: Consider admission if there is at least one of the following criteria:

For women requiring inpatient care, an ultrasound scan should be scheduled to confirm viability, gestational age, and assess for multiple pregnancy or trophoblastic disease.

Use combinations of different drugs if a woman does not respond to a single antiemetic, as different classes can work synergistically.

First-line therapies should be prescribed initially due to extensive safety data. These include anti(H1)histamines, phenothiazines, and doxylamine/pyridoxine.

Second-line therapies include ondansetron and metoclopramide.

Third-line therapy with corticosteroids should be reserved for cases where standard therapies have been ineffective. Use in combination with other antiemetics.

For persistent or severe HG, parenteral, transdermal, or rectal routes may be more effective than oral regimens.

Ginger is not recommended for NVP or HG as evidence shows little or no efficacy and it may cause adverse effects.

There is a lack of consistent evidence that pyridoxine (vitamin B6) alone is an effective therapy for NVP.

To prevent Wernicke encephalopathy, give thiamine (vitamin B1) supplementation to all women admitted with vomiting or severely reduced dietary intake.

Women admitted with HG should be offered thromboprophylaxis with low-molecular-weight heparin (LMWH) due to an increased VTE risk (OR 2.5).

Check urea and serum electrolyte levels daily in women requiring intravenous fluids to manage hyponatraemia and hypokalaemia.

Use histamine type-2 receptor blockers or proton pump inhibitors (PPIs) for women developing gastro-oesophageal reflux disease, oesophagitis, or gastritis.

Question women about their bowel habits and offer laxatives if constipated, particularly if ondansetron is used.

Women should consider avoiding iron-containing preparations if these exacerbate symptoms.

Specialist advice is required for women with co-morbidities like diabetes or a history of bariatric surgery, as malabsorption can increase nutrient deficiency risk.

Normal saline (0.9% NaCl) with additional potassium chloride in each bag is the most appropriate intravenous hydration.

The use of dextrose infusions for fluid replacement is not recommended as it may precipitate Wernicke encephalopathy in thiamine-deficient states.

Assess the severity of symptoms in relation to the woman's quality of life and social situation. Constant nausea is often the most debilitating symptom.

Carry out a full assessment of both physical and mental health status and refer for psychological support if necessary.

Pre-existing mental health conditions may be exacerbated by HG, particularly if oral medications are not tolerated. Consider alternative routes of administration.

Provide information about patient support groups (e.g., Pregnancy Sickness Support) to all women admitted with NVP or HG.

Adopt a holistic, multidisciplinary approach for severe or refractory cases, seeking input from dieticians, mental health teams, and gastroenterology.

When all other medical therapies have failed, consider enteral tube feeding or parenteral nutrition.

All therapeutic measures should be offered and documented before considering termination of pregnancy (TOP).

Women should only be discharged once they are tolerating adequate oral nutrition, hydration, and their prescribed antiemetic therapy.

At discharge, advise women to continue their antiemetics where appropriate and ensure they know how to access further care if symptoms worsen.

Offer serial scans to monitor fetal growth for women with severe NVP or HG who have continued symptoms into the late second or third trimester.

Long-term effects on women: There is no impact on all-cause mortality, but women are at increased risk of postnatal depression, anxiety, and PTSD.

Long-term effects on the child: HG is associated with a small increase in the risk of certain adverse health outcomes (e.g., anxiety disorder, ADHD, autism), though evidence is heterogeneous.

Advice for future pregnancies: Advise women of the high risk of recurrence (15–81%).