Late in pregnancy with bright red vaginal bleeding and no abdominal pain; blood pressure is normal. The most likely diagnosis is

• A. Spontaneous abortion.
• B. Hydatidiform mole.
• C. Placenta previa.
• D. Abruptio placentae.

Answer: (C)

Painless vaginal bleeding in the late third trimester points most strongly to placenta previa. When the placenta implants near or over the cervical os, bleeding can occur suddenly without pain because there isn’t the painful placental separation seen in other conditions. The uterus is typically non-tender and contractions are not the main feature, which fits the scenario described.

In contrast, abruptio placentae usually presents with painful bleeding and a tender, sometimes rigid uterus, often along with hypertension or fetal distress. Spontaneous abortion occurs earlier in pregnancy with cramping and cervical dilation, not in the late third trimester. Hydatidiform mole also tends to present earlier with an enlarged uterus and abnormal hCG levels.

Diagnosis is made via ultrasound to confirm placental location relative to the cervical os. Management centers on maternal and fetal status and usually involves planning delivery by cesarean if placenta previa persists or bleeds late in pregnancy.