Obstetrics & Gynaecology
Question 99 of 180
A woman with severe hyperemesis gravidarum becomes confused, ataxic, and develops nystagmus. Which vitamin deficiency is the most likely cause?
Answer:
Vitamin B1 (thiamine) deficiency may cause potentially life-threatening Wernicke's encephalopathy. Other possible metabolic complications may include:- Weight loss
- Dehydration
- Electrolyte imbalance - such as hyponatraemia, hypokalaemia, or metabolic hypochloraemic alkalosis (if severe, metabolic acidaemia can occur)
- Acute kidney injury
- Abnormal liver function test results - may be secondary to hypovolaemia, malnutrition, and lactic acidosis
- Nutritional and vitamin deficiencies
Nausea and Vomiting in Pregnancy
Obstetrics & Gynaecology
Last Updated: 12th January 2026
Nausea and vomiting in pregnancy (NVP) affects up to 90% of pregnant women and is one of the most common indications for hospital admission among pregnant women. NVP is defined as the symptom of nausea and/or vomiting during pregnancy when onset is prior to 16 weeks of gestation and where there are no other causes. NVP typically starts between the fourth and seventh weeks of gestation, peaks in approximately the ninth week and resolves by the 20th week in 90% of women. (N.B. onset of symptoms after 11 weeks of gestation usually suggests an alternative cause of symptoms unrelated to pregnancy)
Hyperemesis gravidarum (HG) is a severe form of NVP, which affects between 0.3% and 3.6% of pregnant women. HG can be diagnosed when symptoms start in early pregnancy, nausea and/or vomiting are severe enough to cause an inability to eat and drink normally and strongly limits daily activities of living. Signs of dehydration are contributory to diagnosis.
Causes
The exact cause of nausea and vomiting in pregnancy is uncertain, but it is likely to be multifactorial. Possible causative mechanisms include:
- Growth differentiation factor 15 (GDF15)
- The major mechanism of NVP and HG has recently been elucidated to be related to hypersensitivity to the vomiting hormone growth differentiation factor-15 (GDF15).
- Oestrogen
- Nausea and vomiting in pregnancy are more common when estradiol levels are increased. When levels are decreased, nausea and vomiting are less common.
- Evolutionary adaptation
- It has been suggested that nausea and vomiting are a mechanism to prevent the woman eating potentially harmful foods.
- Gastric dysfunction
- In pregnant women, oesophageal, gastric, and small bowel motility are impaired because of smooth muscle relaxation due to increased levels of progesterone. Delayed gastric emptying in pregnancy may also contribute to nausea and vomiting.
Risk Factors
Possible factors associated with the development of nausea and vomiting in pregnancy include:
- Increased placental mass (for example advanced molar gestation, multiple pregnancy)
- First pregnancy
- History of hyperemesis gravidarum in a previous pregnancy
- History of motion sickness
- History of migraines
- Family history (first-degree relative with nausea and vomiting in pregnancy)
- History of nausea with oestrogen-containing oral contraceptives
- Obesity
- Chronic Helicobacter pylori infection
Complications
Maternal and fetal complications are more likely to occur in women with severe vomiting or hyperemesis gravidarum. HG can last for the entire pregnancy, is extremely debilitating and can result in life-threatening physical complications.
Maternal Complications
- Metabolic complications
- Weight loss
- Dehydration
- Electrolyte imbalance - such as hyponatraemia, hypokalaemia, or metabolic hypochloraemic alkalosis (if severe, metabolic acidaemia can occur)
- Acute kidney injury
- Abnormal liver function test results - may be secondary to hypovolaemia, malnutrition, and lactic acidosis
- Nutritional and vitamin deficiencies - vitamin B6 and vitamin B12 deficiency may cause peripheral neuropathy; vitamin B1 (thiamine) deficiency may cause potentially life-threatening Wernicke's encephalopathy
- Mechanical complications
- Gastro-oesophageal reflux disease, oesophagitis, or gastritis
- Retinal haemorrhage
- Splenic avulsion
- Mallory-Weiss tears or oesophageal rupture
- Pneumothorax or pneumomediastinum
- Other complications
- Venous thromboembolism (women with hyperemesis gravidarum in combination with associated immobility and dehydration are at increased risk)
- Fatigue
- Psychosocial - affected women are more at risk of depression, anxiety, emotional distress, post-traumatic stress disorder, and reduced quality of life, 5% of women with hyperemesis gravidarum opt for a termination of pregnancy of an otherwise wanted pregnancy
Foetal Complications
Women with mild-to-moderate symptoms are unlikely to have any negative impact on the foetus. Women with hyperemesis gravidarum and low pregnancy weight gain are at increased risk of preterm delivery, low birthweight, and small-for-gestational age babies.
Assessment
- Ask about:
- The onset, duration, frequency, and severity of symptoms, including impact on oral intake.
- Sleep pattern in a 24-hour period.
- The impact on her mood and emotional wellbeing, how she is coping, support available, and impact on her daily functioning and quality of life including work, home, caring for others, and social activities.
- Additional symptoms such as weight loss, fever, urinary symptoms, headache, neurological symptoms, or abdominal pain, which may indicate an alternative cause for symptoms.
- Any predisposing or risk factors for symptoms, such as previous history, relevant surgical history or family history.
- Any medications prescribed or taken over-the-counter, which may be causing symptoms, such as oral iron or opioids.
- Any comorbidities such as diabetes mellitus or chronic kidney disease (CKD), where symptoms may increase the risk of complications such as diabetic ketoacidosis or acute kidney injury (AKI) respectively.
- Severity Scoring:
- Consider using a validated questionnaire to assess the severity of symptoms, such as the Pregnancy-Unique Quantification of Emesis (PUQE) or Hyperemesis level prediction (HELP) scores. These focus on: nausea, vomiting, ptyalism (hypersalivation), spitting, weight loss, inability to tolerate food and fluids, effect on quality of life and ability to perform daily activities.
- Examination:
- Check temperature (fever may indicate an alternative cause for symptoms).
- Check blood pressure, pulse, and assess for dehydration (suggested by dry mucous membranes, tachycardia, postural hypotension).
- Check oxygen saturation and respiratory rate, for example if a complication is suspected.
- Check weight to assess for weight loss, signs of malnutrition and muscle wasting.
- Perform an abdominal examination to assess for pain or tenderness (may indicate an alternative cause for symptoms).
- Check for any neurological signs such as confusion, nystagmus or ataxia which could indicate Wernicke's encephalopathy.
- Investigations:
- Additional investigations are not needed to confirm the diagnosis if there are mild and uncomplicated symptoms.
- Urinalysis: Nitrites may indicate infection. The presence or absence of ketonuria in pregnancy is not an indicator of dehydration. Assessing urinary ketones does not have a use in the management of NVP or HG and may be misleading.
- MSU (if dipstick indicates signs of UTI)
- Blood tests:
- full blood count (exclude anaemia, infection)
- urea and electrolytes (to guide fluid and electrolyte replacement)
- blood glucose (to exclude diabetes)
- In refractory cases or history of previous admissions, check:
- TFTs: hypothyroid/hyperthyroid
- LFTs: exclude other liver disease such as hepatitis or gallstones, monitor malnutrition
- calcium and phosphate
- amylase: exclude pancreatitis
- VBG: exclude metabolic disturbances to monitor severity
Management
- Women who have nausea and vomiting but are not dehydrated can be cared for in the community with oral antiemetics, reassurance, oral hydration and dietary advice (eat little and often to prevent an empty stomach).
- If women are unable to tolerate oral antiemetics or oral fluids then ambulatory day care management, which provides intravenous fluids, vitamins (especially B1- thiamine) and parenteral antiemetics, is appropriate and should be offered.
- Inpatient care should be considered if there is at least one of the following:
- Continued nausea and vomiting and inability to keep down oral antiemetics
- Continued nausea and vomiting associated with clinical dehydration or weight loss (greater than 5% of body weight), despite oral antiemetics
- Confirmed or suspected comorbidity (such as urinary tract infection and inability to tolerate oral antibiotics).
- Comorbidities such as epilepsy, diabetes, HIV, hypoadrenalism or psychiatric disease where symptoms and inability to tolerate oral intake and medication could present further complications.
- Where inpatient care is required an ultrasound scan should be scheduled to confirm viability and gestational age, and to assess for multiple pregnancy or trophoblastic disease. Unless there are other medical reasons for an urgent scan, this can be scheduled for the next available appointment.
- Pharmacological therapeutic options:
- First line - There are safety data for antiemetics such as anti (H1) histamines (e.g. cyclizine), phenothiazines (e.g. chlorpromazine, prochlorperazine) and pyridoxine-doxylamine (Xonvea®) and they should be prescribed initially when required for NVP and HG.
- Second line - There is evidence that ondansetron is safe. Its use should not be discouraged if first line antiemetics are ineffective. Women can be reassured regarding a very small increase in the absolute risk of orofacial clefting with ondansetron use in the first trimester, which should be balanced with the risks of poorly managed HG.
- Additional second line - Metoclopramide is safe and can be used alone or in combination with other antiemetics.
- For women with persistent or severe HG, the parenteral, transdermal, or rectal route may be necessary and more effective than an oral regimen.
- Corticosteroids should be reserved for cases where standard therapies have been ineffective and used in combination with antiemetics.
- When all other medical therapies have failed to sufficiently manage symptoms, enteral tube feeding or parenteral treatment should be considered with a referral to gastroenterology and a multidisciplinary approach in parallel to ongoing medical therapies.
- Managing complications:
- Normal saline (0.9% NaCl) with additional potassium chloride in each bag, with administration guided by daily monitoring of electrolytes, is the most appropriate intravenous hydration. Urea and serum electrolyte levels should be checked daily in women requiring intravenous fluids.
- Histamine type-2 receptor blockers or proton pump inhibitors may be used for women developing gastro-oesophageal reflux disease, oesophagitis or gastritis.
- Thiamine supplementation (either oral 100 mg tds or intravenous as part of vitamin B complex (Pabrinex®)) should be given to all women admitted with vomiting, or severely reduced dietary intake, especially before administration of dextrose or parenteral nutrition.
- Women admitted with HG should be offered thromboprophylaxis with low-molecular-weight heparin and those being managed in the community should be assessed for VTE risk.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
