Use of gestation adjusted projection method for predicting fetal head circumference

Area of Science:

• Obstetrics and Gynecology
• Fetal Medicine
• Maternal-Fetal Medicine

Background:

• Accurate prediction of fetal head circumference (FHC) is crucial for managing pregnancies and preventing Cesarean deliveries.
• A FHC ≥ 35 cm is a known risk factor for Cesarean delivery.
• The Gestation Adjusted Projection (GAP) method offers a potential tool for predicting FHC.

Purpose of the Study:

• To evaluate the accuracy of the GAP method in predicting birth head circumference (HC_BIRTH) using third-trimester ultrasounds.
• To compare the GAP method's predictive accuracy with direct ultrasound measurements closer to delivery.
• To assess the ability of the GAP method to predict HC_BIRTH ≥ 35 cm, a risk factor for Cesarean delivery.

Main Methods:

• Retrospective chart review of 60 pregnancies.
• Two ultrasounds were performed: one between 32-36 weeks 6 days gestation (period 1) and another within 7 days of birth (period 2).
• FHC was predicted using the GAP method on period 1 data and direct measurement from period 2 data, then compared to HC_BIRTH.

Main Results:

• No significant differences in error measures were found between the GAP method and period 2 ultrasound predictions.
• Both methods demonstrated similar ability in predicting HC_BIRTH ≥ 35 cm.
• The GAP method maintained good performance for deliveries at ≥ 39 weeks, while period 2 ultrasound performance declined.

Conclusions:

• The GAP method applied to early third-trimester ultrasounds predicts HC_BIRTH with accuracy comparable to ultrasounds performed closer to delivery.
• The GAP method may be superior to late-term ultrasounds for predicting HC_BIRTH in pregnancies delivering at ≥ 39 weeks.
• Improved prediction of HC_BIRTH using the GAP method could enhance clinical management of high-risk pregnancies.