VALENCIA, Spain—The 36 weeks competing risks model of the Fetal Medicine Foundation (FMF) for the measurement of small for gestational age (SGA) is also applicable and accurate at 30 to 34 weeks gestation, according to a cohort study, the results of which were presented at the 20th World Congress in Fetal Medicine. It therefore can provide effective risk stratification earlier on.

The cohort study, presented by Ioannis Papastefanou, MD, MSc, PhD, a visiting senior lecturer at King’s College London in the United Kingdom, analyzed more than 3000 women with singleton pregnancies undergoing routine ultrasound examination at 30 to 34 weeks gestation, in 3 prenatal diagnostic centers in Greece. 

The researchers used the default 36 weeks FMF competing risks model to predict SGA, combining maternal factors, estimated fetal weight by ultrasound scan, and uterine artery pulsatility index to calculate the risks for different cutoffs of birthweight percentile and gestational age at delivery. They then assessed the accuracy of the model by means of discrimination and calibration.

The results showed that the prediction of SGA below the third percentile improved when the uterine artery pulsatility index was added and for deliveries closer to the examination.

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Maternal factors, estimated fetal weight, and uterine artery pulsatility index predicted 83.9%, 69.3%, and 66.2% of SGA below the 10th percentile delivered below 37, 40, and 42 weeks, respectively.

The respective figures for SGA below the 3rd percentile were 88%, 74.4%, and 72.8%. 

In terms of population stratification, if the biomarkers used were estimated fetal weight and uterine artery pulsatility index, and the aim was to detect 90% for SGA below the 10th percentile, then 10.8% of the population should be scanned within 2 weeks after the initial assessment, Dr. Papastefanou said. An additional 7.2% should be scanned within 2 and 4 weeks after the initial assessment and an additional 11.7% should be examined within 4 and 6 weeks after the initial assessment, he added.


Papastefanou I. Early prediction and prevention of SGA. Oral presentation at: 20th World Congress in Fetal Medicine; June 27, 2023; Valencia, Spain.