Sonographic examination does not predict twin growth discordance accurately

Area of Science:

• Maternal-fetal medicine
• Prenatal diagnostics
• Twin gestation research

Background:

• Accurate estimation of fetal weight is crucial for managing twin pregnancies.
• Discordant growth in twins, defined as a significant birth weight difference, is associated with adverse outcomes.
• Current ultrasound-based methods for identifying discordant growth have varying degrees of accuracy.

Purpose of the Study:

• To evaluate the accuracy of estimating birth weight in twins with significant discordancy.
• To compare the effectiveness of intra-pair differences in abdominal circumference (delta AC) and estimated fetal weight (delta EFW) in identifying discordant twin growth.

Main Methods:

• Study included 242 non-anomalous twin pairs with gestational ages > 23 weeks.
• Ultrasonographic biometry (AC, HC, FL) was used to estimate fetal weight via Hadlock's formula.
• Likelihood ratios, ROC curves, and prediction limits analyzed the accuracy of delta AC (≥20 mm) and delta EFW (≥25%) for predicting birth weight discordancy (>25%).

Main Results:

• No significant difference in the accuracy of predicting birth weight between the groups.
• Receiver-operating characteristic curves showed areas under the curve not significantly different from the non-diagnostic line for both delta AC and delta EFW.
• A 90% certainty of at least 25% birth weight discordance required delta AC ≥ 172 mm or delta EFW ≥ 112%.

Conclusions:

• Popular methods using delta AC or delta EFW have limited accuracy for predicting discordant twin growth when a 25% birth weight difference is the standard.
• Higher thresholds for delta AC and delta EFW are needed to reliably identify significant birth weight discordancy in twins.