Whilst the majority of women experience nausea (previously termed 'morning sickness') during the early stages of pregnancy it can become problematic in a minority of cases. The Royal College of Obstetricians and Gynaecologists (RCOG) now use the term 'nausea and vomiting of pregnancy' (NVP) to describe troublesome symptoms, with hyperemesis gravidarum being the extreme form of this condition.

It occurs in around 1% of pregnancies and is thought to be related to raised beta hCG levels. Hyperemesis gravidarum is most common between 8 and 12 weeks but may persist up to 20 weeks.


  • Incidence: 13.00 cases per 100,000 person-years
  • Peak incidence: 20-30 years
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+


  • multiple pregnancies
  • trophoblastic disease
  • hyperthyroidism
  • nulliparity
  • obesity

Smoking is associated with a decreased incidence of hyperemesis.

Clinical features


Referral criteria

NICE Clinical Knowledges Summaries recommend considering admission in the following situations:
  • Continued nausea and vomiting and is unable to keep down liquids or oral antiemetics
  • Continued nausea and vomiting with ketonuria and/or weight loss (greater than 5% of body weight), despite treatment with oral antiemetics
  • A confirmed or suspected comorbidity (for example she is unable to tolerate oral antibiotics for a urinary tract infection)

They also recommend having a lower threshold for admitting to hospital if the woman has a co-existing condition (for example diabetes) which may be adversely affected by nausea and vomiting.


The Royal College of Obstetricians and Gynaecologists (RCOG) recommend that the following triad is present before diagnosis hyperemesis gravidarum:
  • 5% pre-pregnancy weight loss
  • dehydration
  • electrolyte imbalance

Validated scoring systems such as the Pregnancy-Unique Quantification of Emesis (PUQE) score can be used to classify the severity of NVP.


  • antihistamines should be used first-line (BNF suggests promethazine as first-line). Cyclizine is also recommended by Clinical Knowledge Summaries (CKS)
  • ondansetron and metoclopramide may be used second-line
  • ginger and P6 (wrist) acupressure: CKS suggest these can be tried but there is little evidence of benefit
  • admission may be needed for IV hydration


  • Wernicke's encephalopathy
  • Mallory-Weiss tear
  • central pontine myelinolysis
  • acute tubular necrosis
  • fetal: small for gestational age, pre-term birth