How stretchy does cervical mucus have to be during the fertile period?

Mucus. Great question… my medical assistant hates when i play with the mucus lol. Did you know that a german doctor years ago built a device to measure exactly that – there must be one in a museum somewhere. The real issue is whether or not the mucus is present, clear and can be stretched like (excuse me) mozzarella cheese. Unfortunately you are 45 years old and if you haven't seen a fertility doctor yet.