Changes in structural brain development after selective fetal growth restriction in monochorionic twins.

Area of Science:

• Neonatal neurology
• Fetal medicine
• Pediatric radiology

Background:

• Fetal growth restriction (FGR) can permanently impact brain development.
• Previous studies comparing FGR singletons to controls have inherent biases.
• Monochorionic twins with selective FGR (sFGR) offer a unique model to study FGR's effects on brain development.

Purpose of the Study:

• To compare neonatal structural cerebral ultrasound measurements within monochorionic twin pairs affected by sFGR.
• To overcome limitations of previous study designs by using a within-pair analysis.

Main Methods:

• Neonatal cerebral ultrasound measurements were compared between smaller and larger twins in monochorionic twin pairs with sFGR (birth-weight discordance ≥ 20%).
• Measurements were also compared to appropriately grown singletons matched for sex and gestational age.
• Data from 58 twin pairs born between 2010 and 2020 were analyzed.

Main Results:

• The smaller twin in sFGR pairs exhibited significantly smaller cerebral structures (corpus callosum, vermis, cerebellum), reduced white/deep gray matter, and smaller intracranial volume compared to the larger twin and singletons.
• A significant correlation was found between birth-weight discordance (BWD) and intracranial-volume discordance (R² = 0.228, P < 0.0001).
• Intracranial-volume discordance was smaller than BWD (19% vs. 32%, P < 0.0001). After adjusting for intracranial volume, only biparietal diameter remained significantly different.

Conclusions:

• Neonatal cerebral ultrasound in monochorionic twins with sFGR demonstrates proportional brain growth restriction in the smaller twin.
• This includes smaller cerebral structures, less gray/white matter, and reduced overall brain size.
• A positive linear relationship exists between BWD and intracranial-volume discordance, with the latter being smaller.