Ay, mahirap talaga sabihin from photos lang mama, pero kung pinkish or brownish with a jelly-like texture siya at parang thick, that's usually the mucus plug na, pero honestly, I'd message your OB or go in for a quick check kasi mas safe na alam mo for sure, especially at 37 weeks na! A few of my mum friends din nag-panic dito so don't worry, your doctor won't mind checking even kung normal discharge lang pala, peace of mind is worth it naman.