SBA — Single Best Answer · Review
Question 203
Delivery suite → Haemorrhage
Classification
Question
SSBAQuestion Header
A woman with recurrent unexplained APH asks whether her low pre-pregnancy BMI is relevant to placental abruption risk. Which response best reflects the guideline?
Question Stem
—
Options
A
Low BMI is a recognised association with placental abruption, but it is not sufficiently predictive to establish or exclude the diagnosis
B
Low BMI is protective because reduced maternal blood volume lowers placental shear stress
C
BMI has no reported association with placental abruption
D
Low BMI is diagnostic of placental insufficiency and therefore diagnostic of abruption
E
BMI is relevant only to placenta praevia
Explanation
Low maternal BMI is a recognised association with placental abruption. As with many epidemiological risk factors in APH, however, its predictive power is limited. The presence of low BMI may increase background risk, but it cannot establish abruption, and a normal BMI would not exclude it. This again reinforces the distinction between epidemiological association and diagnostic performance.
Option Validity
B) Low BMI is not described as protective.
C) Low BMI is a recognised risk factor.
D) A risk factor does not become a diagnostic criterion.
E) Low BMI is associated with an increased risk of placental abruption.
Further Reading
RCOG Green-top Guideline No. 63. Antepartum Haemorrhage. Royal College of Obstetricians and Gynaecologists; 2011.