Aetiology^[1]

Various bacteria, protozoa, viruses and toxins can cause acute gastroenteritis.^[1] Many infections are self-limiting and relatively harmless, but consider those which may be serious for the mother or fetus. In the scenario of a pregnant woman in the UK with acute gastroenteritis symptoms, important pathogens to consider are:

• Infections which may affect the fetus:
  • Listeria spp:^[3]
    • Listeria spp. is a common organism found in soil, dust, water, animal faeces and processed food. It can cross the placenta, perhaps due to its intracellular life cycle.
    • Listeriosis in pregnancy threatens the fetus and newborn through direct infection of the placenta and chorioamnionitis.^[4]
    • Listeriosis affects around 1 in 10,000 pregnancies. Epidemics occur. It is more common in pregnancy than in the general population. Those with reduced immunity are more susceptible (eg, splenectomy, diabetes, steroid use, HIV) - but most cases occur in healthy women.
  • Salmonellosis in pregnancy:
    • There are case reports of intrauterine death, premature delivery and neonatal infection. Early diagnosis and treatment are important.^[5]
• Infections which carry a higher risk of causing severe illness in the mother:
  • Escherichia coli O157.
  • Shigellosis (bacillary dysentery).
  • Clostridium difficile - consider this if there is a history of antibiotics or hospitalisation.
  • Cholera - unlikely in the UK.
  • Note that other infections can cause severe illness in immunocompromised patients - eg, Cryptosporidium spp.
• Parasitic infections which may require specific identification and treatment:
  • Giardia lamblia - may not show up on stool microscopy.
  • Entamoeba spp. - rare in temperate climates.

Assessment

History:

• Symptoms including blood/mucus in stool, fever, vomiting, abdominal pain, oliguria.
• Any other illness; social circumstances and ability to manage oral rehydration at home.
• Travel, contact with animals, contaminated food or water.
• Fetal movements; uterine contractions.

Examination:

• Assess whether the patient is systemically unwell or dehydrated.
• Blood pressure.
• Examine for abdominal tenderness and any signs of an acute abdomen.
• Assess fetal well-being; any signs of premature labour or uterine irritability?
• Urinalysis for glucose, ketones, protein and features of urinary tract infection (blood, nitrites, leukocytes).

Note:

• Consider important differential diagnoses such as ectopic pregnancy or acute appendicitis, where diarrhoea may be a misleading symptom (see 'Differential diagnosis', below).
• As listeriosis in pregnancy is serious and difficult to diagnose, consider it in any pregnant patient presenting with fever, especially if accompanied by flu-like or gastrointestinal symptoms.^[3]

Differential diagnosis

See also the separate article Abdominal Pain in Pregnancy.

• Ectopic pregnancy (a gynaecological emergency) - symptoms include diarrhoea (due to pelvic irritation); signs can be subtle and easily missed.
• Appendicitis - can also present with diarrhoea/vomiting and abdominal pain; more difficult to diagnose in pregnancy.
• Hyperemesis gravidarum.
• Diabetic ketoacidosis.
• Urinary tract infection or pyelonephritis.
• Pre-eclampsia (may cause nausea and epigastric pain).
• Antibiotic-induced diarrhoea.
• Food poisoning due to toxins in food (without infection).
• Inflammatory bowel disease.
• Coeliac disease.

Initial investigations

• Stool sample:
  • Stool samples are advised (whereas for non-pregnant patients this may not be necessary).^[1]
  • Laboratories vary as to which infections are routinely tested for, so always put relevant clinical information on the request form, including the pregnancy, symptoms, travel history and any particular suspected pathogen.
• Blood tests:
  • Renal function and electrolytes if dehydrated.
  • Platelet count is useful if there is suspected haemolytic uraemic syndrome (eg, from E. coli O157).^[6]
  • Blood cultures if systemically unwell or where there is suspicion of Listeria spp.
• Listeria spp:
  • Blood cultures are required.
  • Listeria spp. can also be cultured from CSF or amniotic fluid.^[3]
• Fetal assessment - eg, cardiotocography (CTG) to monitor fetal heart and contractions.
• Further tests if relevant to exclude other causes - eg, urine microscopy, abdominal or pelvic ultrasound.

Management

General points

• Notification and infection control measures may be required.
• Most gastrointestinal infections in pregnancy only require rehydration and fetal monitoring.
• Hospital admission is required for fetal distress, premature labour or significant dehydration.
• Specific antibiotics are rarely required, but may be indicated depending on the results of stool culture and advice from microbiology.

Who needs admission?

Have a lower threshold of admission for pregnant women with gastroenteritis - they are at greater risk of developing dehydration and complications.^[1] Hospital admission may be needed if there is:

• A suspected serious cause requiring investigation/treatment - eg, Listeria spp; E. coli O157.
• Moderate-severe dehydration; or mild dehydration but the patient is unable to manage oral rehydration at home.
• Significant co-existing illness - eg, renal impairment, inflammatory bowel disease, diabetes, immunocompromise, an obstetric problem.

Drug treatment

This will depend on the suspected infection and any microbiology results.

• For 'blind' treatment of travellers' diarrhoea, azithromycin is a suitable antibiotic.^[2]
• Antibiotic treatment is associated with shorter duration of diarrhoea but a higher incidence of side-effects.
• Loperamide is not recommended in pregnancy^[1] and may increase the risk of complications with certain serious gastrointestinal infections - eg, E. coli O157.^[6]

Treatment of listeriosis in pregnancy^[3]

• Penicillin, ampicillin, and amoxicillin have been used most extensively in the treatment of listeriosis.
• Cephalosporins are NOT effective.
• If there is a true penicillin allergy, trimethoprim/sulfamethoxazole is an alternative but there is a teratogenic risk in the first trimester and a risk of neonatal haemolysis and methaemoglobinaemia in the third trimester.^[7] 

Prognosis and complications

In most cases, gastroenteritis during part of the pregnancy probably has no adverse effects on neonatal outcome.^[8] However, possible complications are:

• Febrile illness in pregnancy, which may cause miscarriage or premature labour.
• Severe dehydration which can reduce placental blood flow.
• Listeriosis:
  • May cause intrauterine death or severe neonatal infection.
  • Neonatal infection can cause pneumonia, sepsis, or meningitis.
  • Neonatal presentation varies, but most present with respiratory distress, fever, rash, jaundice, or lethargy. There can be a late-onset illness (2-3 weeks postnatally).^[4]
  • The case fatality rate for fetal or neonatal listeriosis is 20-30%.^[3]
  • The baby should be isolated as may spread infection to others.
• Salmonella spp. - the maternal prognosis is excellent; however, rarely, the fetus may be affected. There are case reports of intrauterine death, premature delivery and neonatal infection.^[5]
• Campylobacter spp. - rarely, this has been linked to fetal death, premature labour or neonatal sepsis (from case reports).^[9] 
• Haemolytic uraemic syndrome may complicate E. coli O157 or Shigella spp. infections.
• Ascending infection with E. coli O157 is a cause of stillbirth.^[10]
• Entamoeba spp. infection was linked to low birth weight in a Tanzanian study.^[11]
• Rarely, Bacillus cereus may cause serious infection in vulnerable neonates. In the cases reported, there was no mention of maternal gastroenteritis, and the infection was transmitted via equipment or nursing staff.^[12]

Prevention

Pregnant women should be advised to practise a high standard of food hygiene - ie:^[13]

• Do not allow frozen food from a shop to defrost before putting it into the freezer; observe the use-by dates.
• Cook all raw food fully; cook eggs until the yolk is set; chilled food must be thoroughly rewarmed.
• Vegetables eaten raw should be washed thoroughly.
• Regular hand-washing, especially after using the toilet, handling animals or soil, and before preparing or eating food; wash hands after handling raw foods.
• Keep raw and cooked food separate (including utensils).
• Do not reheat food more than once.

Advice for preventing listeriosis:^[3]

• Listeria spp. can be transmitted to pregnant women via food. It has been found in a variety of foods at all stages of preparation, from raw to well-cooked left-overs, and will still grow on food that is stored in a fridge. Certain foods should be avoided:
  • Refrigerated pâté or meat spreads (canned ones may be eaten.).
  • Processed and cold meats - eg, hot dogs - unless reheated to steaming hot.
  • Unpasteurised dairy products.
  • Soft cheeses - eg, Brie, Camembert, feta and blue-veined cheeses. (Cheeses that may be eaten include hard cheeses, semi-soft cheeses such as mozzarella, pasteurised processed cheeses, such as slices and spreads, cream cheese and cottage cheese.)
  • Cold, smoked or raw seafood - eg, smoked salmon, shellfish, sashimi (canned seafood may be eaten).
• Pregnant women should not help with lambing or touch lambing products (eg, the placenta).^[13]

Prevention of travellers' diarrhoea may be aided by taking probiotics - eg, lactobacilli; however, their efficacy is still uncertain.^[2]