What is the diagnosis for a 36-year-old woman, gravida (number of times pregnant) 3, para (number of viable births) 2, at 29 weeks gestation, presenting with clear vaginal discharge, increasing over the past 2 days, with no associated vaginal bleeding or contractions, and an amniotic fluid index of 3 cm indicating oligohydramnios (decreased amniotic fluid)?

Differential Diagnosis

• Single most likely diagnosis
  • Premature rupture of membranes (PROM): The patient presents with clear vaginal discharge that increases with Valsalva maneuver, and microscopy shows ferning, which is characteristic of amniotic fluid. The low amniotic fluid index (AFI) of 3 cm also supports this diagnosis.
• Other Likely diagnoses
  • Bacterial vaginosis: Although the patient has been treated for this condition multiple times during the pregnancy, it is possible that she has a recurrence, which could cause an increase in vaginal discharge.
  • Physiologic vaginal discharge: The patient is at 29 weeks gestation, and an increase in vaginal discharge is a common symptom during pregnancy.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Placenta previa: Although the ultrasonography reveals an anterior placenta, it is essential to rule out placenta previa, as it can cause vaginal bleeding and is a life-threatening condition.
  • Uterine rupture: Although the patient has no history of uterine surgery, uterine rupture is a rare but potentially life-threatening condition that should be considered in any patient with abdominal pain or vaginal bleeding during pregnancy.
• Rare diagnoses
  • Cervical insufficiency: This condition can cause an increase in vaginal discharge and is associated with preterm labor and pregnancy loss.
  • Amniotic fluid embolism: Although this condition is rare, it is a life-threatening emergency that should be considered in any patient with sudden onset of symptoms such as vaginal bleeding, abdominal pain, or cardiorespiratory distress.