Fever of unknown origin in pregnant women

Fever of unknown origin in pregnant women: A complex diagnostic challenge

Fever of unknown origin (FUO) is a clinical situation in which the patient has a prolonged fever, the cause of which cannot be identified using standard diagnostic methods. In pregnant women this condition is especially challenging because the diagnostic workup is limited by the need to avoid procedures potentially harmful to the fetus (e.g., certain radiation-based imaging methods).

Definition of FUO in pregnant women

The general definition of FUO includes a temperature above 38.3°C lasting more than 3 weeks without an established diagnosis after intensive evaluation. For pregnant women these criteria are more flexible, but the essence is the same: a prolonged fever without an obvious cause. This situation automatically classifies the pregnancy as high risk.

Main directions of diagnostic search

As in the general population, the causes of FUO in pregnant women are divided into three major groups. The physician will sequentially rule out diseases from each group.

• Infectious diseases: This is the most common cause. The search is aimed at detecting hidden infection foci such as abscesses, tuberculosis, cytomegalovirus infection, toxoplasmosis, listeriosis.
• Autoimmune (systemic) diseases: Systemic lupus erythematosus, Still's disease and other rheumatologic conditions can debut during pregnancy with fever.
• Oncologic diseases: Lymphomas and leukemias are the most common oncologic cause of FUO.

Diagnosis is a painstaking process that includes numerous blood tests for various infections and autoimmune markers, bacterial cultures, and safe imaging methods (ultrasound, MRI). Occasionally, the cause may be recurrent fevers associated with autoinflammatory syndromes. For general mechanisms, read the article "Fever of unknown origin".