Yes, it is one of the signs of labour. During the early part of labor, your body begins to release prostaglandins, a group of hormonelike substances that cause the uterus to contract and help soften and dilate the cervix. But prostaglandins can also hyperstimulate the bowels, causing frequent stools or even diarrhea, Dr. Grabowski says. http://www.parents.com/pregnancy/giving-birth/signs-of-labor/labor-signs/
The hormones which contract the uterus also cause diarrhoea. Diarrhoea was the first sign of labour for me. http://www.motherandbaby.co.uk/pregnancy-and-birth/birth/getting-ready-for-birth/the-early-labour-signs-you-need-to-look-out-for
thanks
Chanty Sanderson