TOPLINE:

Universal ultrasound scan around 35-36 weeks detected 63% of neonates born severely small for gestational age (SGA), yet most stillbirths and neonatal complications occurred in foetuses classified as normal appropriate for gestational age (AGA) at the time of scan.

METHODOLOGY:

• Researchers conducted a retrospective population-based cohort study to evaluate how antenatally diagnosed foetal growth restriction (FGR) ultrasound phenotypes, identified at a universal late third-trimester scan, contribute to adverse perinatal outcomes, including stillbirth and neonatal complications.
• They included 45,179 women with singleton pregnancies from the UK, dated by the crown-rump length, who underwent a universal ultrasound scan between 35 + 1 and 36 + 6 weeks, with estimated due dates between 2016 and 2023.
• Foetuses were classified into five mutually exclusive ultrasound phenotypes: International Society of Ultrasound in Obstetrics and Gynecology (ISUOG)-defined FGR, constitutional SGA with an estimated foetal weight (EFW) below the 10th centile, AGA with abnormal Dopplers, AGA with reduced abdominal circumference growth velocity below the 10th centile, and normal AGA.
• Primary outcomes were stillbirth and a composite of severe adverse outcomes, defined as at least one of the following: stillbirth or neonatal death within 28 days, grade 2 or 3 neonatal encephalopathy, or therapeutic cooling or mechanical ventilation at term for more than 24 hours.
• Secondary outcomes were severe SGA with a birth weight below the third centile and neonatal unit admission.

TAKEAWAY:

• Overall, 54 (0.12%) stillbirths and 253 (0.56%) composite adverse outcomes were recorded; normal AGA foetuses accounted for 79.6% of stillbirths and 81% of composite adverse outcomes.
• The absolute risk for stillbirth (0.08%-0.21%) and composite adverse outcomes (0.52%-0.73%) was broadly similar across all five phenotype groups.
• Foetuses with an ISUOG-defined FGR phenotype carried the highest risk for severe SGA (odds ratio, 27.1; 95% CI, 22.43-32.80), whereas AGA foetuses with abnormal Dopplers or reduced abdominal circumference growth velocity showed a modest increase in the risk; overall, the 36-week scan detected about 62.7% of neonates born severely SGA.
• Those neonates classified as normal AGA had most (78.2%) neonatal unit admissions.

IN PRACTICE:

"In a population universally screened for FGR around 36 weeks, most adverse outcomes occur in women with a normal result. This does not imply that the scan is ineffective, for the detection rate of severe SGA is high and the risk of adverse outcomes in pregnancies with accepted 'abnormal' findings was similar to those without," the authors wrote.

SOURCE:

This study was led by Elena D'Alberti, University of Oxford, Oxford, England. It was published online on March 08, 2026, in BJOG: An International Journal of Obstetrics & Gynaecology.

LIMITATIONS:

Intervention patterns and small numbers of severe outcomes limited statistical comparisons across different FGR phenotypes. The study did not use population-based charts to classify both EFW and birth weight, potentially causing lower-than-expected proportions of severe SGA. Additionally, a notable proportion of stillbirths remained unexplained.

DISCLOSURES:

This study was supported by the Oxford Hospitals Charity. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.