FETAL HEAD MEASUREMENTS

 

 

 

 

 

 

BIPARIETAL DIAMETER (BPD)

Biparietal Diameter (BPD) = widest transverse diameter of the fetal head.

Landmarks

 

Skull has an ovoid shape and the Biparietal Diameter (BPD) is 80-90% of the Occipitofrontal Diameter (OFD)

 

Measurement

Biparietal diameter (BPD) (Table) – Chervenak et.al 1992

Biparietal diameter (BPD) (Table) – Hadlock et.al. 1984

Biparietal diameter (BPD) (Table) – Romero et.al. 1988

Biparietal diameter (BPD) (Graph) – Chervenak et.al 1992

Biparietal diameter (BPD) (Graph) – Hadlock et.al. 1984

Biparietal diameter (BPD) (Graph) – Romero et.al. 1988

 

 

Variability

( +/- 2SD)

12-18 wks
18-24 wks
24-30 wks
30-36 wks
36-42 wks

+\- 1.2 wks
+\- 1.7 wks
+\- 2.2 wks
+\- 3.1 wks
+\- 3.2 wks

 

Precision of predictors of Gestational Age

Disadvantage of BPD is that it disregards the shape of the cranium. i.e. two heads of equal widths but different lengths will have the same BPD's, but the longer head will have a greater corrected BPD or HC than the shorter head.

 

CORRECTED BPD

 

 

REFERENCES