Ultrasonic growth patterns in normal and discordant twins

Area of Science:

• Maternal-Fetal Medicine
• Obstetrics
• Perinatology

Background:

• Conflicting conclusions exist regarding twin biparietal diameter (BPD) growth.
• Establishing definitive criteria for normal vs. abnormal twin growth is crucial for multiple pregnancies.

Purpose of the Study:

• To establish definitive criteria for normal and abnormal growth in multiple pregnancies.
• To utilize both ultrasonic biparietal diameter (BPD) and newborn anthropometric data.

Main Methods:

• Comparison of fetal BPD and newborn head circumference in concordant twins with appropriate for gestational age (AGA) singletons.
• Application of singleton standards to evaluate twin BPD growth.
• Development of ultrasonic criteria for diagnosing discordancy: intrapair BPD difference ≥5 mm and head circumference difference >5%.

Main Results:

• Fetal BPD and newborn head circumference in concordant twins mirrored singleton AGA standards across all gestational ages.
• Singleton standards are applicable for assessing twin BPD growth, including in the third trimester.
• Discordant BPD growth before the third trimester is linked to twin-transfusion syndrome and high perinatal mortality.
• Divergent BPD growth starting after 30 weeks' gestation shows a better prognosis.

Conclusions:

• Singleton standards are reliable for evaluating twin biparietal diameter growth.
• Specific ultrasonic criteria can diagnose twin growth discordancy.
• Timing of BPD divergence in twins has significant implications for perinatal outcomes and management strategies.