Differential Diagnosis for Painless Bleeding in Pregnancy

Single Most Likely Diagnosis

• Placenta Previa: This condition is characterized by the placenta partially or completely covering the internal cervical os, leading to painless vaginal bleeding in the second or third trimester. It is a common cause of antepartum hemorrhage and is often diagnosed via ultrasound.

Other Likely Diagnoses

• Placental Abruption: Although typically associated with painful bleeding, a placental abruption can sometimes present with painless bleeding, especially if the abruption is marginal or the patient has a high pain threshold.
• Uterine Rupture: While more commonly associated with severe pain, a uterine rupture can occasionally present with painless bleeding, particularly if the rupture is incomplete or the patient is under anesthesia.

Do Not Miss Diagnoses

• Vasa Previa: A condition where fetal blood vessels are exposed in the lower uterine segment, unprotected by Wharton's jelly, and at risk of rupture. This can lead to rapid fetal exsanguination and is often associated with painless vaginal bleeding.
• Uterine Atony: Postpartum hemorrhage due to uterine atony can sometimes be painless, especially if the patient has received adequate pain management. It's crucial to consider this diagnosis in the postpartum period.

Rare Diagnoses

• Choriocarcinoma: A rare malignant tumor that can cause painless vaginal bleeding during pregnancy due to its potential to invade the uterus and cause bleeding.
• Uterine Arteriovenous Malformation (AVM): A rare vascular anomaly that can cause painless vaginal bleeding due to the abnormal connection between arteries and veins within the uterus.