The primary aim of this observational, prospective, exploratory study is to evaluate the effect of NNS on GER pH-MII features in preterm infants (GA ≤32 weeks) symptomatic for GER (i.e. suffering from frequent regurgitations, feeding difficulties, failure to thrive and/or post-prandial desaturations) for which a 24-hour pH-MII monitoring for GER diagnostic evaluation has been scheduled.