Ultrasonographic Criteria for Biparietal Diameter (BPD) Measurement

Abstract

Ultrasonography has proved to be an accurate, safe, fast, reliable, and cost effective Imaging modality for the estimation of gestational age. Assessment The BPD remains the standard against which other parameters of gestational age are compared. The BPD should be measured as early as possible after 13 weeks for dating. The BPD is useful for dating a pregnancy and in estimating intrauterine fetal weight in weight equation. This study was carried out at the Fattah Alrahman Albashier centre, and police hospital in the Sudan, and Bisha Central Hospital- Aseer Saudi Arabia from November 2005 to February2006 to evaluate the relative accuracy of BPD in measuring fetal age.

One hundred and ninety three healthy pregency age between 18 - 40 years were examined by ultrasound during gestational age 12-40 weeks with normal and well being ,singleton fetuses. Using an Aloka (SSD-650), Aloka1100 real times scanners with convex transducer with frequency 3.5 MHz.

The study results shows Biparietal Diameter ( BPD ) is very accurate during second trimester especially between the 12- 24 weeks last menstrual period (LMP) with accuracy only

One week plus or minus . Accuracy between 25 – 31 weeks LMP ( + ) or ( - ) ten days . Accuracy between 31- 36 weeks LMP , tow weeks ( + ) or ( - ) . Accuracy after 33 weeks LMP is three weeks ( + ) or ( - ) . The study recommended that if there is no evidence of fetal head anomalies it is best to use the Biparietal Diameter (BPD ) measurement for evaluation of gestational age in the second trimester up to 31 week LMP , alone or with combination of others parameters ( Femur Length –FL- or Abdominal circumference AC ) . After 33weeks LMP , it is better to use other parameters (Femur Length -FL-) , because the Biparietal Diamter measurement is not accurate ( + or - three weeks )