NCIt definition : Labor without the use of pharmacological and/or mechanical interventions to initiate
labor. Does not apply if artificial rupture of membranes is performed before the onset
of labor. (reVITALize);
Alternative definition : NICHD: Labor without the use of pharmacological and/or mechanical interventions to
initiate labor. Does not apply if artificial rupture of membranes is performed before
the onset of labor. [verbatim from reVITALize];