Hyperemesis gravidarum consists of the most common cause of persistent severe nausea and vomiting before 20 weeks of pregnancy and the most common cause of hospitalization during the first half of pregnancy

Hyperemesis gravidarum consists of:

●          Persistent severe nausea and vomiting

●          Before 20 weeks

●          Ketosis

●          Weight loss, (>5% of pre-pregnant weight)

Hyperemesis gravidarum affects about 1% of pregnancies, compared to the much more common occurrence of “morning sickness” (milder nausea and vomiting) which occurs in up to 70% of pregnancies.


Vomiting in pregnancy is related to the effects of human chorionic gonadotrophin produced by the placenta.

The nausea and vomiting associated with pregnancy:

●          Almost always begins by 9-10 weeks of gestation.

●          Peaks at 11-13 weeks.

●          Resolves (in the majority of cases) by 12-14 weeks.

●          May continue beyond 20-22 weeks and in some cases, until delivery, in up to 10% of pregnancies.

Despite the label “morning sickness”, symptoms are not confined to the morning.

Hyperemesis gravidarum is severe and intractable nausea and vomiting in pregnancy as defined above.


  1. Idiopathic.
  • Hyper-placentosis

●          Multiple pregnancy

            ●          Diabetes

            ●          Rhesus Isoimmunization.

  • Hydatidiform mole
  • Less commonly, UTI, Hepatitis


Vomiting in late pregnancy is more significant and may indicate other complications of pregnancy.

Complications include:

1.         Dehydration

Severe vomiting can result in more rapid deterioration of pregnant patients than compared with non pregnant patients, particularly in late pregnancy.     

2.         Electrolyte abnormalities.

3.         Mallory-Weiss tears

4.         Gastric acid reflux with oesophagitis.  

5.         Wernicke’s encephalopathy, in severe cases, without thiamine supplementation.

6.         Patients with hyperemesis gravidarum often demonstrate abnormalities of liver enzymes. The reason for this is uncertain

Clinical Assessment

Assess the degree of dehydration.

Hyperemesis gravidarum is a diagnosis of exclusion. It is important to consider and rule out other possible causes of vomiting such as bowel obstruction.


●          Vomiting twice or more per day

●          Ketones 1 +

●          Requires anti-emetics


●          Vomiting twice or more per day

●          Ketones 2 + or more

●          Requiring IV rehydration

●          Weight loss.


Blood tests:

1.         FBE

2.         U&Es / glucose

3.         LFTs.

●          Elevated transaminase levels may occur in as many as 50% of patients with           hyperemesis. (Other causes for elevated liver enzymes should also be kept in          mind, however)

4.         TSH:

●          Hyperemesis is associated with hyperthyroidism and suppressed TSH levels in      50-60% of cases.

5.         BHCG

            ●          If excessively high consider multiple pregnancy or hydatidiform mole.


MSU for M&C, to exclude UTI

FWT to test for the presence of Ketones


Consider an ultrasound to evaluate for:

●          Multiple pregnancy

●          Trophoblastic disease


1.         IV fluid rehydration.

●          Give as clinically indicated

2.         Electrolyte disturbances:

●          Correct any hypokalemia is required

3.         Antiemetic therapy:

Mild symptoms:

Milder symptoms may be controlled with oral medication.

            Options include: 1

            ●          Pyridoxine (vitamin B6)

50mg orally up to four times a day or 200mg orally at night.

            If symptoms not controlled add

            ●          Doxylamine (a H1 antagonist), (category A) 2

12.5 mg orally nocte, increase to 25 mg nocte then add 12.5mg mane and afternoon as required.

If symptoms not controlled add another sedating antihistamine:

●          Promethazine (Phenergan) (category C) 2

            10 to 25mg orally three to four times a day


●          Dimenhydrinate (Dramamine), (category A) 2        

                        50 mg orally three to four times a day.

            If still not improving add either:

            ●          Metoclopramide (category A) 2

                        10 mg orally three times a day.

Note that latest recommendations now limit the daily dosage to 30 mg and the duration of dosage to 5 days. 3


            ●          Prochlorperazine (category C)

5 to 10 mg orally two to three times a day or 25mg PR once to twice a day.

            Moderate to severe symptoms:

            ●          Ondansetron (Zofran) (category B1) 2

                        4 mg orally b.d or tds.

                        4 mg IV/IM every 8-12 hours.


            ●          Metoclopramide (category A

                        10mg IV/IM every 8 hours.


            ●          Prochlorperazine

                        12.5 mg IM every 8 hours.


            ●          Promethazine

                        12.5 -25 mg IM every 4-6 hours.


            ●          Chlorpromazine (category C) 2

                        25-50 mg IV/IM every 6-8 hours, (maximum 75 mg daily)

An ultimate option also includes oral steroids, but these should only be prescribed in consultation with the Obstetric unit.

4.         Antacids:

Some cases may be associated with distressing reflux and oesophagitis symptoms. 

            Simple antacids, (e.g. Mylanta, Gaviscon) 

            ●          These are considered as first line therapy.


●          This H2-receptor antagonist is classified as a category B1 drug with respect to       pregnancy.

It is safe for use in pregnancy, and is generally used as second line therapy after antacids.


●          Most proton pump inhibitors (PPIs) are listed by the Therapeutic Goods     Administration (TGA) as category B3 agents with respect to pregnancy, and as   such are considered third line therapy after antacids and H2 antagonists.   

Observational studies have not indicated any increased risk of adverse pregnancy outcomes with PPI use.

If a woman is taking a PPI and is planning pregnancy, consider switching to an H2-receptor antagonists, or trialling on-demand PPI therapy, at least for the first trimester.

If a PPI is required during pregnancy, the greatest clinical experience is with omeprazole.

5.         Thiamine

●          Consider thiamine in severe cases, (100 mg orally daily) to prevent the possible complication of Wernicke’s encephalopathy.

Continue treatment until patient can tolerate oral fluids and urine shows little or no ketones.


In milder cases IV rehydration in the ED over several hours may be tried with reassessment after this.

If the patient is then well and the vomiting has settled the patient may be discharged with an early review by their General Practitioner

In more significant cases of vomiting the patient will require admission.

If the patient requires admission but is not too unwell, an SSU admission may be appropriate.




Fellowship Notes

Dr Jessica Hiller LITFL Author

Doctor at Sir Charles Gairdner Hospital in Western Australia. Graduated from Curtin University in 2023 with a Bachelor of Medicine, Bachelor of Surgery. I am passionate about Obstetrics and Gynaecology, with a special interest in rural health care.

Physician in training. German translator and lover of medical history.

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