Objective: To evaluate the progression of Doppler abnormalities in fetuses with late-onset fetal smallness (SGA) that become growth restricted (FGR).
Methods: 524 Doppler examinations of the umbilical and cerebral arteries systems, belonging to 442 late-onset SGA fetuses after week 34, were studied, evaluating by means of the statistical difference with the respective abnormal centiles, the pattern of progression into abnormal Doppler values and the distribution and cumulative sum of Doppler anomalies according to the interval to delivery.
Results: Only one third (33.5%, N = 148) of late-onset SGA fetuses presented Doppler anomalies, suggesting that most were of constitutional origin. The most frequent progression pattern into abnormal Doppler (N = 127, 85.81%) was that in which only one system (umbilical or cerebral) became abnormal. Half of fetuses debuted with abnormal umbilical flow (52%, N = 77) and half with cerebral anomalies (47.97%, N = 71), which were more likely to appear later and at shorter intervals to delivery (p = .007). These progression patters defined two varieties of late-onset FGR (type I and II) with similar outcome but different birth weight centiles (BW centile = 2.51, SD 2.91 versus 3.97, SD 3.17, p < .01).
Conclusion: Two thirds of late-onset fetal smallness occurs without hemodynamic changes. In half of the remaining cases an initial cerebral vasodilation defines a group of fetuses with similar outcome but higher BW centile.
Keywords: Fetal hemodynamics; fetal middle cerebral artery; fetal umbilical artery; fetal vertebral artery; late-onset fetal growth restriction; small for gestational age.