ABSTRACTSubjectThis study investigates the placental autophagic activity in growth‐restricted fetuses in the monochorionic (MC) twin model.Patients and methodsForty MC twins were prospectively enrolled in this study, including 21 with and 19 without selective intrauterine growth restriction (sIUGR), defined as birth weight below the tenth percentile. The sIUGR group was subdivided on the basis of present versus absent or reversed umbilical artery end‐diastolic flow at Doppler. Placenta samples were taken after delivery from each twin placenta territories. After protein extraction, Western blot was used to determine light chain 3 (LC3)‐II placental protein expression in sIUGR and appropriately grown (appropriate‐for‐gestational age, AGA) twins.ResultsThe LC3‐II was significantly higher in the sIUGR twin placental territory than in their AGA counterparts. In the sIUGR group, LC3‐II fold change was significantly increased compared with that in the AGA cotwins (2.28 vs 1.04, p < 0.05). Placental LC3‐II protein expression was particularly stimulated in the MC sIUGR group with abnormal umbilical artery Doppler flow compared with AGA controls (p < 0.05, one‐way analysis of variance test).ConclusionsIn MC twins, the placental autophagic activity is different between sIUGR and AGA cotwins. The placenta territory with the least blood flow perfusion has the highest autophagic activity. © 2013 John Wiley & Sons, Ltd.