The Relation between Head Circumference and Mid-Pelvic Circumference: A Simple Index for Cephalopelvic Disproportion...

Area of Science:

• Obstetrics and Gynecology
• Medical Imaging
• Fetal Medicine

Background:

• Cephalopelvic disproportion (CPD) is a frequent obstetric complication.
• Evaluating fetal head circumference (HC) against maternal pelvic dimensions may aid CPD prediction.
• The study explored the ratio of HC to pelvic circumference (PC) as a potential CPD predictor.

Purpose of the Study:

• To assess the proof-of-concept for using the ratio between fetal head circumference and maternal pelvic circumference as a predictor of cephalopelvic disproportion.
• To investigate the correlation between the cephalopelvic circumference index (CPCI) and Cesarean delivery due to CPD.

Main Methods:

• Retrospective analysis of 104 deliveries (84 normal vaginal deliveries, 20 Cesarean deliveries for CPD).
• Abdominopelvic CT scans were used to reconstruct maternal pelvis dimensions.
• Neonatal head circumference (HC) served as a proxy for fetal HC; the ratio HC/PC × 100 was calculated as CPCI.

Main Results:

• The mid-pelvis CPCI (MP-CPCI) was significantly larger in the Cesarean delivery group (103 ± 11%) compared to the normal vaginal delivery group (97 ± 8%).
• Each 1% increase in MP-CPCI was independently associated with an 11% increased likelihood of Cesarean delivery for CPD (aOR 1.11).
• The adjusted odds ratio for Cesarean delivery due to CPD increased substantially with rising MP-CPCI values.

Conclusions:

• The MP-CPCI is a simple metric reflecting fetal HC and maternal PC dimensions.
• MP-CPCI shows potential in distinguishing patients at lower versus higher risk of CPD.
• Further prospective studies are needed to validate prenatal pelvimetry and MP-CPCI for predicting CPD risk during labor.