Differential Diagnosis for Fishy Vaginal Discharge in Pregnancy

• Single Most Likely Diagnosis
  • Bacterial Vaginosis (BV): This is the most common cause of fishy vaginal discharge in pregnant women. BV is characterized by an imbalance of the normal vaginal flora, with a decrease in lactobacilli and an increase in anaerobic bacteria, leading to the production of amines that cause the fishy odor.
• Other Likely Diagnoses
  • Trichomoniasis: A sexually transmitted infection caused by the protozoan Trichomonas vaginalis, which can also cause a fishy-smelling vaginal discharge.
  • Vulvovaginal Candidiasis: Although typically associated with a yeasty odor, some cases can present with a fishy smell, especially if there is a mixed infection.
• Do Not Miss Diagnoses
  • Chorioamnionitis: An intrauterine infection that can cause preterm labor and other serious complications. While not typically the primary presentation, any abnormal vaginal discharge in pregnancy should prompt consideration of this diagnosis to prevent severe outcomes.
  • Placenta Previa or Abruption: Although these conditions are more commonly associated with bleeding, any vaginal discharge or bleeding in pregnancy should prompt an evaluation for these potentially life-threatening conditions.
• Rare Diagnoses
  • Desquamative Inflammatory Vaginitis (DIV): A rare condition characterized by a purulent vaginal discharge, which can sometimes have a fishy odor, and is associated with significant vaginal inflammation.
  • Foreign Body: The presence of a foreign body in the vagina can cause a foul-smelling discharge due to the accumulation of bacteria and debris around the object. This is less common but should be considered, especially in cases where other diagnoses have been ruled out.