NORMAL VARIANTS

• Accuracy of BPD is based on head shape.
• Cephalic Index = BPD/FOD x 100 = 78.0 +/- 8 (2 SD).
• Value below normal i.e. unusually long head = Scaphocephaly or dolicocephaly.
• Oligohydramnios
• Intrauterine demise

• Value above normal i.e. unusually short head = Brachycephaly
• Premature closure of lambdoid or coronal sutures.
• Increased frequency of fetal trisomies esp. 18, 21, and 13.
• Corrected BPD- Area corrected BPD = BPDa = BPD x FOD/1.265.
• Head circumference.