MRI outperforms Ultrasound at identifying the Large for Gestational Age (LGA) fetus

Estimated Fetal Weight (EFW) = Clinically important

Large for Gestational Age (LGA, EFW >95th) fetus

→ Birth complications

LGA diagnosis = ↑chance of intervention

As per Big Baby Trial, diagnosis of LGA by UltraSound Scan (USS)

has large variation

& false positives 60% (Gardosi et al, 2025)

There is emerging evidence that MRI may be more accurate

at predicting fetal weight, particularly where EFW >95th centile

compared to USS.

As part of the currently recruiting MibirthResearch Study

(www.mibirthstudy.com) 131 singleton participants, between 35+5 and 40+6

weeks gestation, had the following scans within 48 hours of each other (80%

were same day):

1. Antenatal fetal growth USS

2. MRI (0.55Tesla)

In this small cohort, we show that MRI has PPV = 1 (100%) in identifying the LGA

fetus

Within the cohort it is also apparent that correct identification of ‘missed LGA’ may

have changed the clinical outcome in 2 cases.

Further data (n=500) will be collected in Mibirth study.