Preterm birth, occurring in nearly 8 % of pregnancies, is associated with increased risk of neonatal morbidity and mortality, and with intellectual and developmental consequences for the infants who survive [1,2]. Among preterm infants, birthweight has been identified as a critical predictor of neonatal outcomes. During the antenatal period, especially before 32 weeks of gestation, sonographic-estimated fetal weight (EFW) serves as a surrogate for birthweight, thus facilitating informed discussions concerning perinatal morbidity and mortality [3]. EFW also impacts antenatal management, the timing of delivery, and the method of delivery for women at risk of preterm birth [4].

Limited research has explored the accuracy of EFW as a predictor of actual birthweight in very preterm infants (<32 weeks). A small study revealed that EFW tended to overestimate the birthweight of infants delivered during the periviable period, spanning from 23 0/7 to 27 6/7 weeks of gestation [3]. The investigators also reported that EFW was less precise for infants born small for gestational age (SGA) than appropriate for gestational age (AGA). A study of 93 fetuses born in the periviable period failed to establish any clinically significant correlation between the accuracy of EFW and the actual birthweight [5].

As very preterm infants, especially those who are SGA, face the greatest risks of adverse neonatal outcomes, the limitations of our prenatal methods in predicting birthweight should be examined particularly for this population [6]. The purpose of our study was to examine the accuracy of EFW to predict birthweight in very preterm infants. Moreover, as SGA infants face increased risks for adverse outcomes, we aimed to compare the accuracy of EFW between very preterm infants who were SGA and those who were AGA.