<prompt> Ceain sign of onset of labor: March 2013Labor painsShowDilatation of internal osFormation of bag of waters  <response>: Ans. D i.e. Formation of bag of waters The first symptom to appear is intermittent painful uterine contractions followed by expulsion of blood stained mucus show per vaginum But formation of bag of membranes is almost a ceain sign of onset of labor 