Objective: To investigate the relation between the biochemical markers of umbilical venous erythropoietin and umbilical arterial pH and morphologic placental abnormalities in fetal hypoxia.
Methods: Placentas from 300 high-risk newborn infants (gestational age 24-42 weeks) were examined macroscopically and microscopically following standardized criteria. The morphologic findings were correlated with the erythropoietin concentration in umbilical venous blood and with umbilical arterial pH at birth. Venous hematocrit and circulating nucleated red blood cells were measured in 112 of these infants during the first 6 hours of life.
Results: The umbilical venous erythropoietin concentration correlated significantly (r = 0.74) with the number of circulating nucleated red blood cells. In 26 placentas without morphologic abnormalities, the median (and 25th and 75th percentiles) erythropoietin concentration was 35.2 mU/mL (19.2-48.7) and umbilical arterial pH was 7.30 (7.20-7.33). The erythropoietin concentration was elevated significantly when placental examination showed evidence of acute villous circulatory disturbance (61.3 mU/mL; 24.2-125.1), fetal vasculopathy (85.6 mU/mL; 23.7-119.7), or chorioamnionitis with fetal reaction (51.3 mU/mL; 27.7-118.7). The erythropoietin concentration varied significantly with the stage of placental meconium phagocytosis; it was 62.7 mU/mL (16.3-125.9) if meconium phagocytosis was classified as recent, 128.2 mU/mL (44.4-1483.2) if it was classified as a few hours old, and 66.2 mU/mL (46.3-140.1) if it was classified as a few days old. Umbilical arterial pH was not altered significantly with different morphologic placental abnormalities.
Conclusions: Fetal erythropoietin production is stimulated by hypoxia after a few hours' delay and leads to increased erythropoiesis. Placental examination combined with measurement of umbilical venous erythropoietin and umbilical arterial pH provides information about earlier fetal hypoxia.