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TOPLINE:

Assessing the risk for small for gestational age (SGA) at mid-gestation (19 + 0 to 23 + 6 weeks) using maternal risk factors together with the estimated foetal weight and uterine artery pulsatility index (UtA-PI) could identify pregnancies requiring monitoring at 26, 30, and 33 weeks, complementing a routine 36-week ultrasound scan.

METHODOLOGY:

• Researchers conducted a prospective, non-intervention study to predict the risk for SGA at mid-gestation by combining maternal risk factors with the estimated foetal weight and UtA-PI.
• They included 134,443 women with singleton pregnancies who underwent routine ultrasound scans at 19 + 0 to 23 + 6 weeks of gestation between January 2011 and May 2024.
• Different risk cutoffs were used to detect approximately 80%, 85%, and 90% of cases of delivery with SGA at < 28, < 32, and < 36 weeks of gestation, respectively.
• Outcomes of interest were the delivery of SGA neonates with birth weight less than 10th or 3rd percentile at < 28, < 32, and < 36 weeks of gestation.

TAKEAWAY:

• Among singleton pregnancies, 12.51% delivered SGA neonates with birth weight less than 10th percentile, including 0.15% at < 28 weeks, 0.42% at < 32 weeks, and 1.33% at < 36 weeks.
• Similarly, 5.15% of pregnancies delivered SGA neonates with birth weight less than third percentile, including 0.11%, 0.33%, and 0.92% at < 28, < 32, and < 36 weeks, respectively.
• Screen positive rates for detecting 80% of SGA neonates with birth weight less than 10th percentile were 9.5% at < 28 weeks, 19.6% at < 32 weeks, and 29.6% at < 36 weeks.
• Similarly, screen positive rates for detecting 80% of SGA neonates with birth weight less than third percentile were 6.5%, 13.0%, and 21.6% at < 28, < 32, and < 36 weeks, respectively.

IN PRACTICE:

"Future research should focus on the clinical implementation of the proposed stratification plan offering timely ultrasound scans after 24 weeks, according to the second trimester integrated risk assessment. The targeted ultrasound scans between 24 to 36 weeks gestation may improve the management of SGA pregnancies," the authors wrote.

SOURCE:

This study was led by Ioannis Papastefanou, MD, Fetal Medicine Research Institute, King's College Hospital, London, England. It was published online on June 12, 2025, in the American Journal of Obstetrics and Gynecology.

LIMITATIONS:

The study results were limited to only singleton pregnancies. Risk cutoffs for assigning the population into each of the three management groups will vary according to the local resources and preferences. Spanning over 13 years, changes in antenatal care during this period may have influenced the findings; however, second trimester measurements, techniques, or distributions for foetal biometry and UtA-PI remained consistent.

DISCLOSURES:

This study was supported by a grant from the Fetal Medicine Foundation. 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.