An analysis of 40 placental samples representing different gestational stages showed ( 1 ) no significant differences in beclin-1 , DRAM , and LC3B-II levels in placentas between early and mid-gestation , and late gestation with vaginal delivery ; ( 2 ) placentas from late gestation with cesarean section had lower levels of LC3B-II compared to early and mid-gestation , and late gestation with vaginal delivery ; levels of DRAM were also lower compared to placentas from early and mid-gestation ; and ( 3 ) using explant cultures , villous tissues from early and late gestation had similar rates of autophagic flux under physiological oxygen concentrations .