We studied the consequences of misdiagnosis of intrauterine growth retardation (IUGR) for preterm elective cesarean section among live singleton newborns in two teaching hospitals in Paris between 1978 and 1983. The population studied comprised the 16,540 babies who were normal for date, according to the 10th percentile of the reference curve established in this population. For 118 of these infants, IUGR had been diagnosed during pregnancy. The preterm elective cesarean section rate was 12.7% among newborns for whom IUGR was erroneously diagnosed, compared to 1.2% among those for whom IUGR was not diagnosed. The relationship between preterm cesarean section and misdiagnosis of IUGR still existed (odds ratio: 5.2, 95% CI: 2.1–12.9) after taking into account obstetric history and hypertension during pregnancy. Our results show that after diagnosis of IUGR, supplementary tests are essential to confirm fetal distress and consequently avoid unnecessary interventions.