Reduced fetal growth velocity and weight loss are associated with adverse perinatal outcome in fetuses at risk of growth restriction

Background: While fetal size is associated with adverse perinatal outcome, the relationship between fetal growth velocity and adverse perinatal outcome is unclear. Objectives: To evaluate the relationship between fetal growth velocity and signs of cerebral blood flow redistribution, and their association with birthweight and adverse perinatal outcome. Study design: Secondary analysis of the TRUFFLE 2 multicentre observational prospective feasibility study of fetuses at risk of fetal growth restriction between 32+0 and 36+6 weeks (n=856) evaluated by ultrasound biometry and umbilical and middle cerebral artery Doppler. Individual fetal growth velocity was calculated: from the difference of birthweight and estimated fetal weight at three, two and one week before delivery; and by linear regression of all available estimated fetal weight measurements. Fetal estimated weight and birthweight were expressed as absolute value and as multiple of the median for statistical calulation. The coefficients of the individual linear regression of estimated fetal weight measurements (growth velocity; grams/week) were plotted against the last umbilical-cerebral ratio with sub-classification for perinatal outcome. The association of these measurements with adverse perinatal outcome was assessed. The adverse perinatal outcome was a composite of abnormal condition at birth or major neonatal morbidity RESULTS: Adverse perinatal outcome was more frequent among fetuses whose antenatal growth was <100 grams/week, irrespective of signs of cerebral blood flow redistribution. Infants with birthweight <0.65 multiple of the median were enrolled earlier, had the lowest fetal growth velocity, higher umbilical-cerebral ratio and were more likely to have adverse perinatal outcome. A decreasing fetal growth velocity was observed in 163 (19%) women in whom the estimated fetal weight multiple of the median regression coefficient was <-0.025, and in these umbilical-cerebral ratio values were higher and the adverse perinatal outcome more frequent. Sixty-seven of these women (41%; 8% of total group) had negative growth velocity. Estimated fetal weight and umbilical-cerebral ratio at admission and fetal growth velocity combined by logistic regression had a higher association with adverse perinatal outcome than any of these parameters separately (relative risk 3.3; 95% confidence ratio 2.3-4.8). Conclusions: In fetuses at risk of late preterm fetal growth restriction, reduced growth velocity is associated with an increased risk of adverse perinatal outcome, irrespective of signs of cerebral blood flow redistribution. Some fetuses showed negative growth velocity suggesting catabolic metabolism.