How do doctors (ob's) check to see if your water has broken? what do they look for?

Physical exam: Your doctor will do a speculum exam and look for a pool of amnionic fluid in the vagina, a nitrazine test that checks the ph of the fluid and will put some of the fluid on a slide and look under the microscope for a ferning like pattern that the fluid will make. In certain circumstances that are very rare, your doctor could do an amniocentesis and place dye in the fluid around the baby.