RESUMO
OBJECTIVE: To compare the fatty acid phospholipid composition of the umbilical artery and the placenta in cases of fetal growth retardation (FGR) and of normal growth, as well as in symmetric and asymmetric FGR. DESIGN: Case-control study. SETTING: University hospital. POPULATION: Thirty-nine FGR cases (12 asymmetric, 27 symmetric) and 78 cases with normal growth. MAIN OUTCOME MEASURES: Thin layer gas-liquid capillary chromatography of phospholipid fatty acids in umbilical artery and placental cotyledons. Newborns were classified as FGR if their weight was under the 10th percentile for our center. FGR was defined as symmetric if the ponderal index was >2.32, and as asymmetric if it was <2.32. RESULTS: In FGR, arachidonic acid was significantly increased both in placenta (24.05%+/-2.78 vs 22.46%+/-2.93) and in umbilical artery (16.76%+/-2.40 vs 15.58%+/-3.67). Indeed this increase was significantly higher in asymmetric than in symmetric FGR (25.70+/-2.32 vs 23.32+/-2.68 in placenta and 18.06+/-1.46 vs 16.14 +/-2.53 in umbilical artery). On the other hand, in the placenta there were a number of differences in the metabolic ratios analyzed when comparing symmetric and asymmetric FGR, indicating a lower DHA availability and a higher n-6 fatty acid elongation and desaturation in asymmetric FGR. CONCLUSION: FGR is characterized by an increase in arachidonic acid both in the placenta and umbilical artery phospolipids, probably reflecting a different mobilization from tissue stores. It is speculated that the different arterial composition could be partially responsible for the increased cardiovascular risk of FGR in adulthood. On the other hand the metabolic status of the placenta concerning polyunsaturated fatty acids was very different in symmetric and asymmetric FGR, suggesting a different pathogenesis.