Objective: To examine the relationship between umbilical artery (UA) end-diastolic flow and neonatal thrombocytopenia.
Methods: We prospectively examined 115 anatomically normal single fetuses with UA pulsatility indices more than two standard deviations above the gestational age mean and subsequent birth weights below the tenth percentile. Peripheral neonatal platelet counts in fetuses with positive UA end-diastolic velocity were compared with those of fetuses with absent or reversed UA end-diastolic velocity.
Results: Sixty-seven fetuses (58.3%) had positive UA end-diastolic velocity and 48 (41.7%) had absent or reversed UA end-diastolic velocity. Three neonates in the positive-flow group and 22 neonates in the absent- or reversed-flow group had platelet counts of less than 100, 000/mm(3) (relative risk 10.2; 95% confidence interval; 3.2, 32.3; P <.001). Absent or reversed end-diastolic velocity had a sensitivity of 88%, specificity of 71%, positive predictive value of 46%, and negative predictive value of 96% for predicting neonatal thrombocytopenia. Neonates with absent or reversed flow also had lower median platelet counts (101,500/mm(3) versus 208,000/mm(3), P <.001), hemoglobin levels (15.1 versus 16.4 g/dL, P <.01), and hematocrits (47.6 versus 51.1%, P <.05), as well as higher nucleated red blood cell counts (191 versus 15 per 100 white blood cells, P <. 001).
Conclusion: Absent or reversed UA end-diastolic velocity in growth-restricted fetuses is associated with a statistically significant increase in risk of neonatal thrombocytopenia.