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Listeriosis in pregnancy

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Listeriosis can occur at any time in pregnancy. Patients may be asymptomatic, only being diagnosed after developing problems around delivery, or in the neonate.

  • in a case series of listeriosis in pregnancy (2)
    • 32% of women had symptoms of a flu-like illness
    • 65% had a fever
    • other symptoms included backache (21.5%) (which may be mistaken for a urinary tract infection)
    • headache (10.5%)
    • vomiting/diarrhea (7%)
    • muscle pains (4%)
    • sore throat (4%)
    • approximately 29% of the women were asymptomatic

Listeriosis occurs in 6-15/100,000 pregnancies.

Generally, perinatal infection occurs in the second or third trimester.

Diagnosis is made on the basis of clinical picture and blood culture.

Summary listeriosis:

Reservoir:

  • gastrointestinal tracts of humans, birds, cattle, sheep and other animals
  • widespread in the environment: soil, vegetation, water, silage/sewage, mammal/fish/bird faeces
  • occurs in raw foods, food components and ready to eat foods: most commonly in foods because of contamination from sites in food production environments
  • due to a listeria outbreak linked to smoked fish, people at higher risk of serious infection should only eat smoked fish products that have been thoroughly cooked (4)
    • when cooking smoked fish products at home, make sure they are steaming hot all the way through

Epidemiology:

  • listeriosis is a rare but severe systemic infection that includes bacteraemia, meningitis, encephalitis and in pregnant women can lead to miscarriage and stillbirth
  • most often affects those who have a weakened immune system including pregnant women, their unborn and new born infants, the elderly and individuals who are immunocompromised by a pre-existing medical condition or treatments for an existing illness
  • occasionally, healthy people can become infected
  • Listeriosis has a high mortality rate of 20-30% and in the UK is the most common cause of death from a foodborne illness. The annual number of laboratory-confirmed cases of listeriosis averaged 180 a year between 2005-14

Transmission:

  • majority of cases are foodborne. Cases and outbreaks have been associated with a variety of foodstuffs, the most common in England and Wales being pre-prepared sandwiches but other foods have included soft cheeses, cooked and processed meats (e.g. pâté and sliced meat), smoked fish, butter, olives and melon in the US
  • mother-to-baby transmission is important:
    • in utero transmission,
    • vertical transmission during birth, or
    • person-to-person spread soon after delivery
  • direct contact with infected animals can occasionally cause infection
  • pregnant women, individuals who are immunocompromised and those (< 1 month and >60 years of age) are more susceptible to infection
  • L. monocytogenes can be present in the faeces of approximately 5% of the population but is likely to be transitory

Incubation period

  • For invasive disease, the incubation period ranges from 1-70 days

Clinical Features:

  • initial symptoms of listeriosis include fever and flu-like symptoms, which may or may not be preceded by a febrile gastroenteritis. Pregnant women may be asymptomatic or have mild symptoms. A person of any age and immune-state may experience any of the following symptoms or remain asymptomatic. Below are the most common presentations for particular patient groups
  • Healthy adults and older children:
    • Asymptomatic infection
    • Acute gastroenteritis with fever
    • Non-specific symptoms such as fever, muscle aches, headache
    • (often goes undiagnosed/unrecognised)
  • Pregnant women
    • no/mild non-specific flu-like symptoms (as above)
    • foetal loss, stillbirth, pre-term delivery with severe infection in the newborn (some with pre-term delivery) and neonatal meningitis
  • Immunosuppressed persons / older adults
    • septicaemia, meningitis or meningo-encephalitis
  • Immunocompetent persons can also present with severe disease such as septicaemia or meningitis

Infectivity:

  • Not applicable except at and shortly after delivery due to contact (hand or fomites) from an infected infant to an apparently healthy infant who develops meningitis

Reference:

  • Benshushan A et al. Listeria infection during pregnancy: a 10 year experience. Isr Med Assoc J. 2002 Oct; 4(10):776-80.
  • Mylonakis E et al.Review Listeriosis during pregnancy: a case series and review of 222 cases.Medicine (Baltimore). 2002 Jul; 81(4):260-9
  • PHE (2019). Recommendations for the Public Health Management of Gastrointestinal Infections
  • NHS Conditions. Listeriosis (Accessed 27/4/22)

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