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Abnormal development of the placental vasculature is responsible for maternal and fetal impacts of uteroplacental insufficiency.1 Umbilical artery (UA) Doppler allows the non-invasive assessment of the severity of this vascular abnormality. UA end diastolic velocities are positive in mild placental insufficiency but are absent or reversed if 60–70% of the tertiary villous vessels are damaged. This observational study examines the relation between UA end diastolic velocity in growth restricted fetuses and haematological indices at birth. Singleton growth restricted neonates (birth weight < 10th centile) had a complete blood count within two hours of delivery. Results were related to the UA end diastolic velocity.
Among 179 participants, UA end diastolic velocity was positive in 108 fetuses (60%), absent in 26 (14%), and reversed in 45 (25%). Progressive abnormality of the UA waveform was associated with significant effects on white cell, red cell, and platelet counts (table 1).
White blood cell and nucleated red blood cell counts correlated positively (r = 0.56, p < 0.001) and were most strongly associated with base deficit and birthweight centile (p < 0.05). The platelet count was predominantly determined by UA blood flow resistance, and red blood cell indices by birthweight centile. Interestingly, the nucleated red blood cell count showed a negative correlation with the haemoglobin concentration (r = −0.28, p < 0.001) and platelet count (r = −0.31, p < 0.001).
Our results indicate that neonatal haematological consequences of placental insufficiency are complex and go beyond the expected polycythaemic response to intrauterine hypoxaemia.2 With increasing severity of placental dysfunction, enhanced red cell numbers in response to hypoxaemia are no longer observed, and metabolic compromise may even be associated with decreased red cell mass, thrombocytopenia, and increased nucleated red blood cells and white blood cells. UA Doppler is useful for identifying growth restricted neonates at high risk for these haematological disturbances.
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