The bleeding in placenta previa originates primarily from which site?
- A Rupture of spiral arterioles at the placental bed
- B Opening up of maternal venous sinuses at the placental margin as the lower segment forms and stretches ✓
- C Tear of velamentously inserted fetal vessels
- D Laceration of the cervix during effacement
Correct answer: B. Opening up of maternal venous sinuses at the placental margin as the lower segment forms and stretches
Explanation
As the lower uterine segment forms and expands in late pregnancy, the inelastic placenta previa shears away from the underlying wall, tearing thin-walled maternal venous sinuses at its margins. Venous blood at low pressure explains why previal hemorrhage is painless and rarely fatal initially. Spiral arteriole rupture relates to abruption, velamentous vessel tearing defines vasa previa with fetal blood, and cervical laceration is a traumatic postpartum event.
Reference: DC Dutta Textbook of Obstetrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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