Placenta aging early?

When is it considered early aging? I'm being induced at 37 weeks due to my daughter measuring 3 weeks behind and being in the 13th percentile. At 33 weeks they said the placenta looked like it was beginning to age. I'm 35 (almost 36) weeks now and they are still saying early induction.

Is 33 weeks considered too early for the placenta to start aging?