  We examine the quantum loop effects on the single-field inflationary models
in a spatially flat Friedmann-Robertson-Walker (FRW) cosmological space-time
with a general self-interacting scalar field potential, which is modeled in
terms of the Hubble flow parameters in the effective field theory approach. In
particular, we focus on the scenarios in both slow-roll to ultra-slow-roll
(SR-USR) and SR-USR-SR inflation, in which it is shown that density
perturbations originated from quantum vacuum fluctuations can be enhanced at
small-scales, and then potentially collapse into primordial black holes (PBHs).
Here our estimates indicate significant one-loop corrections around the peak of
the density power spectrum in both scenarios. The induced large quantum loop
effects should be confirmed by a more formal quantum field theory, and, if so,
should be treated in a self-consistent manner that will be discussed.
