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Objective: Fetal growth surveillance includes assessment of size as well as rate of growth, and various definitions for slow growth have been adopted into clinical use. The aim of this study was to evaluate the effectiveness of different models to identify stillbirth risk, in addition to risk represented by the fetus being small‐for‐gestational age (SGA). Methods: This was a retrospective analysis of a routinely collected and anonymized dataset of pregnancies that had two or more third‐trimester ultrasound measurements of estimated fetal weight (EFW). SGA was defined as EFW < 10th customized centile, and slow growth was defined according to five published models in clinical use: (1) a fixed velocity limit of 20 g per day (FVL20); (2) a fixed > 50 centile drop, regardless of scan‐measurement interval (FCD50); (3) a fixed > 30 centile drop, regardless of scan interval (FCD30); (4) growth trajectory slower than the third customized growth‐centile limit (GCL3); and (5) EFW at second scan below the projected optimal weight range (POWR), based on partial receiver‐operating‐characteristics‐curve‐derived cut‐offs specific to the scan interval. Results: The study cohort consisted of 164 718 pregnancies with 480 592 third‐trimester ultrasound scans (mean ± SD, 2.9 ± 0.9). The last two scans in each pregnancy were performed at an average gestational age of 33 + 5 and 37 + 1 weeks. At the last scan, 12 858 (7.8%) EFWs were SGA, and of these, 9359 were also SGA at birth (positive predictive value, 72.8%). The rate at which slow growth was defined varied considerably (FVL20, 12.7%; FCD50, 0.7%; FCD30, 4.6%; GCL3, 19.8%; POWR, 10.1%), and there was varying overlap between cases identified as having slow growth and those identified as SGA at the last scan. Only the POWR method identified additional non‐SGA pregnancies with slow growth (11 237/16 671 (67.4%)) that had significant stillbirth risk (relative risk, 1.58 (95% CI, 1.04–2.39)). These non‐SGA cases resulting in stillbirth had a median EFW centile of 52.6 at the last scan and a median weight centile of 27.3 at birth. Subgroup analysis identified methodological problems with the fixed‐velocity model because it assumes linear growth throughout gestation, and with the centile‐based methods because the non‐parametric distribution of centiles at the extremes does not reflect actual difference in weight gain. Conclusion: Comparative analysis of five clinically used methods to define slow fetal growth has shown that only the measurement‐interval‐specific POWR model can identify non‐SGA fetuses with slow growth that are at increased risk of stillbirth. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Objective: To produce a customized birthweight standard for Iran.Method: Retrospective study of a pregnancy database collected from five hospitals across Iran. The cohort consisted of 4994 consecutive term births with complete data, delivered between July 2013 and November 2014. Coefficients were derived using a backwards stepwise multiple regression technique.Results: Maternal height, weight in early pregnancy and parity as well as the baby's sex were identified as significant physiological variables affecting birthweight. Paternal height and weight were also significant although weaker factors. The expected 280-day birthweight, free from pathological influences, of a standard size mother (height 163 cm, weight 64 kg) in her first pregnancy was 3390 g. Pathological factors found to affect birthweight in this cohort included village housing, anemia, preexisting and gestational diabetes and preeclampsia.Conclusion: The analysis confirmed the main physiological variables that affect birthweight in other countries and shows paternal factors also to be significant variables. Development of a country-specific customized birthweight standard will aid clinicians in Iran to distinguish between fetuses that are either constitutionally or pathologically small, thereby avoiding unnecessary interventions, and improving identification of at-risk pregnancies and perinatal outcome. [ABSTRACT FROM AUTHOR]