Management of the growth-restricted fetus: the role of noninvasive tests and fetal blood sampling

OBJECTIVE: To assess the accuracy of two noninvasive tests, the nonstress test (NST) and Doppler velocimetry of the umbilical artery, in predicting fetal acidemia or hypoxia demonstrated by funipuncture, and to determine any association between acidemia or hypoxia and perinatal outcome. METHODS: The study included 112 consecutive growth-restricted fetuses diagnosed by ultrasonography between 26-39 weeks' gestation. For Doppler sonograms, the absence of end-diastolic flow was considered pathologic. Acidemia and hypoxia were defined as a pH and an oxygen pressure (PO2) below the fifth percentile at the given gestational age. The fetuses were classified according to the results obtained by the different tests (Doppler velocimetry, NST, cord blood gases). RESULTS: Fetuses with one or both noninvasive tests abnormal (group A, N = 32) had a significantly lower mean gestational age at sampling than those fetuses with both noninvasive tests normal (group B, N = 80). Mean pH and PO2 values for groups A and B were significantly different. Obstetric and perinatal data were collected, and a statistically significant difference was demonstrated between those with a pH and/or PO2 below the fifth percentile and those with a pH and PO2 above the fifth percentile for all indices except birth weight below the tenth percentile. CONCLUSION: Fetal growth restriction is a benign condition in physically normal fetuses if both noninvasive tests and pH and PO2 measured by funipuncture are normal in the absence of maternal pathology. One single fetal blood analysis for pH and PO2 helped separate groups having different obstetric and neonatal outcomes.

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