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Nausea and vomiting of pregnancy

NVOP, often referred to as morning sickness, is a common condition affecting the majority of pregnancies. It typically presents in the first trimester and is characterized by mild-to-moderate nausea and vomiting. HG is a more severe form of NVOP characterized by excessive, persistent nausea and vomiting leading to dehydration, electrolyte imbalance, weight loss, and hospital admission.
The pathophysiology of NVOP is not fully understood, but it is believed that a combination of hormonal changes, gastric dysrhythmias, and heightened olfactory and gustatory sensitivity may contribute to its development. Pregnancy-related hormones such as progesterone, estrogen, and hCG have been widely studied, and other hormones such as leptin, placental GH, prolactin, thyroid, and adrenal cortical hormones have also been implicated. Additionally, infectious, immunological, psychological, metabolic, and anatomical factors may also play a role in its onset.
Nausea during pregnancy is reported in about 50-80% of individuals, with nausea and vomiting occurring in approximately 50%, and HG affecting about 0.3-3% of pregnant individuals.
Disease course
Clinically, NVOP is characterized by mild-to-moderate nausea and vomiting, typically developing in the first trimester of pregnancy. HG is distinguished by severe nausea and vomiting leading to dehydration, orthostatic symptoms, metabolic and electrolyte imbalance, weight loss, and eventually necessitate hospital admission. Both NVOP and HG can significantly impact the patient's QoL due to persistent symptoms.
Prognosis and risk of recurrence
The prognosis of NVOP is generally good, with symptoms often resolving with lifestyle and dietary changes, and more severe cases responding to safe and effective treatments. The prognosis of HG is more variable, with some patients experiencing symptoms throughout their pregnancy.
Key sources
The following summarized guidelines for the evaluation and management of nausea and vomiting of pregnancy are prepared by our editorial team based on guidelines from the Royal College of Obstetricians and Gynaecologists (RCOG 2024), the European Association for the Study of the Liver (EASL 2023), the American Academy of Family Physicians (AAFP 2023; 2014), the American College of Gastroenterology (ACG 2016), and the Society of Obstetricians and Gynaecologists of Canada (SOGC 2016).


1.Screening and diagnosis

Diagnose NVOP when onset is before 16 weeks of gestation and other causes of nausea and vomiting have been excluded.
Consider diagnosing HG when symptoms start in early pregnancy and nausea and/or vomiting are severe enough to cause an inability to eat and drink normally and strongly limit daily activities of living. View signs of dehydration as contributory to diagnosis.
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2.Classification and risk stratification

Severity assessment: consider using an objective and validated index of nausea and vomiting, such as the PUQE and HyperEmesis Level Prediction tools, to classify the severity of NVOP and HG.
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3.Diagnostic investigations

Initial evaluation
Elicit history, perform a physical examination, and obtain an evaluation for the assessment of NVOP and HG.
Obtain ultrasound to confirm viability and gestational age and to assess for multiple pregnancy or trophoblastic disease in patients requiring inpatient care. Consider scheduling this for the next available appointment unless there are other medical reasons for an urgent ultrasound.

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  • Liver tests

4.Medical management

Setting of care: as per RCOG 2024 guidelines, manage patients with mild NVOP in an outpatient setting with antiemetics.
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  • Antiemetics

  • Pyridoxine and doxylamine

  • Thiamine

  • Corticosteroids

  • Rehydration therapy

  • Thromnoprophylaxis

  • Management of constipation

  • Management of gastroesophageal reflux

5.Nonpharmacologic interventions

Psychosocial care: assess the severity of the impact of symptoms on the QoL and social situation in patients with NVOP or HG.
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  • Cognitive therapy

  • Nutritional support

  • Iron preparations

  • Ginger

  • Acupressure

6.Therapeutic procedures

Termination of pregnancy: attempt all therapeutic measures before considering termination of pregnancy.

7.Patient education

General counseling: counsel patients with NVOP to eat whatever pregnancy-safe food appeals to them, and encourage lifestyle changes liberally.

8.Preventative measures

Primary prevention: as per RCOG 2024 guidelines, advise early lifestyle/dietary modifications and offer antiemetics that were useful in the index pregnancy to reduce the risk of NVOP or HG in the current pregnancy.

9.Follow-up and surveillance

Discharge from hospital
Discharge patients only when the following are met:
appropriate antiemetic therapy has been tolerated
adequate oral nutrition and hydration have been tolerated
management of concurrent conditions has been completed
Advise patients to continue antiemetics where appropriate and ensure they know how to access further care at the time of discharge.

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  • Follow-up