Estimating fetal age: effect of head shape on BPD

Area of Science:

• Obstetrics and Gynecology
• Medical Imaging
• Fetal Development

Background:

• Accurate estimation of fetal age is crucial for optimal pregnancy management.
• Biparietal diameter (BPD) is a common ultrasound biometric for gestational age assessment.
• Variations in fetal skull shape can influence BPD measurement accuracy.

Observation:

• Sonographic examinations revealed that dolichocephaly and brachycephaly can affect BPD measurements.
• Cephalic index (CI) values in affected fetuses fell outside typical ranges.
• Normal in utero CI values were established from 316 sonographic studies (mean 78.3).

Findings:

• A CI outside 1 SD from the mean (CI < 74 or CI > 83) may indicate altered BPD measurements.
• Significant deviations in CI suggest potential inaccuracies in BPD-based gestational age estimation.
• Head circumference (HC) provides a more reliable alternative for gestational age assessment in cases of atypical fetal head shape.

Implications:

• Clinicians should consider fetal skull shape when interpreting BPD measurements.
• Utilizing HC may improve gestational age accuracy in fetuses with dolichocephaly or brachycephaly.
• This research refines ultrasound protocols for fetal age determination, enhancing obstetric care.