Background Information

Definition

Nausea and vomiting in pregnancy (NVP): nausea and/or vomiting during pregnancy that begins <16 weeks of gestation, provided no other causes are present

Hyperemesis gravidarum is a severe form of NVP, where nausea and/or vomiting are severe enough to cause:

• An inability to eat and drink normally, and
• Strong limitations on daily activities of living

Epideimology

Mild to moderate NVP is very common and can be considered a normal, physiological part of pregnancy. It affects up to 90% of pregnant women.

Mild to moderate NVP does not negatively impact the developing fetus and may even have a protective effect on the pregnancy.

Aetiology

The primary cause of NVP and hyperemesis gravidarum is linked to hypersensitivty to GDF-15 – a vomiting hormone produced when placental genes are activated

• hCG is no longer believed to be the causative factor
• GDF-15 is responsible for causing taste aversion, loss of appetite, nausea, vomiting, and weight loss

Key risk factors:

• Genetic factors (variations affecting the expression of the GDF-15)
• Previous history of NVP or hyperemesis gravidarum
• Multiple pregnancies (e.g. twins)
• Trophoblastic disease (including molar pregnancy and choriocarcinoma)
• Chronic H. pylori infection

Clinical Features

NVP and hyperemesis gravidarum usually begin at 4-7 weeks of gestation and peak at ~9 weeks. Symptoms usually resolve by 20 weeks (in ~90% women).

Symptoms:

• Nausea
• Vomiting
• Inability to tolerate food and fluids
• Hypersalivation and spitting

Complications

Metabolic complications

• Dehydration (e.g. tachycardia, hypotension, tachypnoea, dry lips and mouth, oliguria or anuria)
• Weight loss
• Electrolyte imbalance – hyponatraemia, hypokalemia, metabolic hypochloraemic alkalosis
• Acute kidney injury
• Nutritional and vitamin deficiencies
  • Vitamin B1 deficiency → life-threatening Wernicke’s encephalopathy
  • Vitamin B6 and B12 deficiency → peripheral neuropathy

Complications of severe vomiting:

• Retinal haemorrhage
• Mallory-Weiss tears / oesophageal rupture
• Pneumothorax / pneumomediastinum
• Splenic avulsion
• GORD / oesophagitis, gastritis

Diagnosis

Diagnostic Criteria

NVP and hyperemesis gravidarum are clinical diagnoses, supported by biochemical findings listed below.

Investigation and Assessment

History and clinical examination should include:

• Temperature, blood pressure, pulse, oxygen saturation, respiratory rate, and weight
• Abdominal and neurological examination

Recommended investigations:

• Urinalysis (if urinalysis indicates UTI → send MSU)
• Blood tests
  • FBC
  • U&E
  • Blood glucose
• Ultrasound – to confirm a viable intrauterine pregnancy and assess for multiple pregnancy / trophoblastic disease
• Consider TFT, LFT, amylase, calcium, phosphate and venous blood gas in refractory cases / history of previous admissions

Biochemical findings and trends:

Severity Assessment

The Pregnancy-Unique Quantification of Emesis (PUQE) tool can be used to classify the severity:

• ≤6 = mild
• 7-12 = moderate
• 13-15 = severe

Management

Admission Criteria

Inpatient care should be considered if ANY of the following is present:

• PUQE score ≥13
• Failed outpatient management

Refer for inpatient management if ANY of the following is present:

• Inability to tolerate oral intake
• Clinical dehydration
• >5% weight loss despite oral antiemetics
• Presence of co-morbidities (e.g. epilepsy, diabetes, HIV, hypoadrenalism, psychiatric disease)
• Concerns regarding mental health

Inpatient vs Outpatient Care

Inpatient care should involve:

• Rehydration with IV 0.9% saline with additional potassium (dextrose is NOT recommended)
• Thiamine supplementation (oral or Pabrinex®)
• Thromboprophylaxis with LMWH (alternative: graduated compression stockings)

If inpatient care is not indicated, offer the following conservative care as an outpatinet@

• Rest as needed
• Avoid sensory stimuli (e.g. odours, heat, noise)
• Eat plain biscuits / crackers in the morning
• Bland, small, frequent protein-rich meals, low in carbohydrate and fat
• Drink little and often
• Acupressure (e.g., over P6 point)

Apart from those above, see the anti-emetic therapy section below, which should be offered in both inpatient and outpatinet care.

Anti-Emetic Therapy

References