Objectives: To determine the longitudinal trends and rates of conversion of normal to abnormal uterine (UtA), umbilical (UA) and middle cerebral artery (MCA) Doppler velocimetry throughout the third trimester in late-onset small-for-gestational-age (SGA) fetuses.
Methods: UtA, UA and MCA Doppler velocimetry was serially performed in a cohort of singleton consecutive late-onset SGA fetuses with normal Doppler values at diagnosis. The rate of conversion of normal to abnormal Doppler values was evaluated by survival analysis. Longitudinal trends were modeled by means of multilevel analysis.
Results: A total of 616 scans were performed on 171 SGA fetuses. Mean gestational age at inclusion and at delivery was 34.1 (SD 1.6) and 38.7 (SD 1.7) weeks, respectively. The proportions of abnormal UtA (2.3 vs. 4.1%) and UA (2.3 vs. 2.9%) pulsatility index (PI) were not significantly different between 37 weeks and before delivery. On the other hand, the proportions of abnormal MCA-PI (4.1 vs. 13.5%) and cerebroplacental ratio (CPR) (7 vs. 22.8%) were significantly different between these two examinations. The remaining proportion of cases with normal UtA-, UA- and MCA-PIs and CPR at 40 weeks were 98.6, 94.5, 85 and 49.6%, respectively. Whereas a slight increasing trend was observed for the UtA-PI (β = 0.002) and UA-PI (β = 0.01), MCA-PI (β = 0.044) and CPR (β = 0.124) showed a progressive decrease until delivery.
Conclusions: Late-onset SGA fetuses with normal Doppler velocimetry upon diagnosis show progression from 37 weeks' gestation with worsening CPR followed by a decrease in MCA-PI.
Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.