Diagnostic Value of Blood Sampling in Fetuses With Growth Retardation

Abstract

Intrauterine growth retardation (IUGR) is an important cause of perinatal mortality and morbidity. Growth-restricted infants have a greater risk of handicap later in childhood. No proven intrauterine therapy is available for these fetuses. Delivery is usually chosen as the best treatment. The timing of delivery is based on electronic fetal heart rate monitoring, amniotic fluid volume, fetal behavior and, occasionally, on amniotic fluid studies for lung maturity. This study was designed to determine whether funipuncture might provide additional information useful for management. The study series included 58 consecutive fetuses with IUGR diagnosed by ultrasonography between 26 and 37 weeks of gestation. Ultrasonographic measurements of the head and abdominal circumferences of these fetuses were below the 5th percentile of reference values for fetuses of similar ages. All 58 fetuses had normal karyotypes and none had malformations detected at birth. A control group of 61 normal fetuses that underwent funipuncture between 17 and 39 weeks of gestation for prenatal diagnosis was used to compare. All of the control fetuses were normal. Fetal blood was obtained from the umbilical vein. The wave form of the fetal umbilical artery blood flow was measured by Doppler velocimetry immediately before blood sampling. Likewise, the fetal heart rate was recorded immediately before blood sampling. The fetuses with growth retardation were divided into three groups according to their fetal heart rates and the pulsatility indices of the umbilical artery. Group 1 consisted of 21 fetuses with normal heart rates and pulsatility indices. Group 2 consisted of 24 fetuses with normal heart rates and pulsatility indices more than 2.0 SD above the mean in the normal fetuses. Group 3 consisted of 11 fetuses with abnormal heart rates and pulsatility indices more than 2.0 SD above the normal mean in the normal fetuses. In this series, an abnormal fetal heart rate was invariably associated with an abnormal pulsatility index. None of the 21 fetuses with normal heart rates and velocimetry had hypoxia or acidosis. Of the 24 fetuses with normal heart rates and abnormal velocimetry, four (17 per cent) had moderate lactic acidosis. One had a low pH value (4 per cent). Forty (12 per cent) had hypoxia. Of the 11 fetuses with abnormal heart rates and velocimetry, 7 (63 per cent) had lactic acidosis, low blood oxygen content, and low pH values. A similar number of fetuses in all three groups had elevated hemoglobin concentrations. The authors conclude that assessment of fetal oxygenation and acid-base balance is not indicated in growth-restricted fetuses if their electronic fetal heart rate monitoring and Doppler velocimetry are normal. They suggest that if the results of velocimetry are abnormal, fetal blood sampling can distinguish fetuses that have growth retardation alone from those that have hypoxia and acidemia along with growth restriction. They speculate that this might aid in determining the optimal time of delivery.