Hi, my 4 year old female is having her first litter and developing the mamary glands and all other signs of a hopeful pregnancy. Today for the first time I saw a thick string of almost clear mucous hanging from her vulva.....I think I read somewhere here before that this is a good sign for pregnancy????? If not should I take her in for a low grade antibiotic like Baytril?????? Thanks,

It is normal.

Sounds normal to me. If it's clear then it isn't an infection so no need for antibiotics. IMHO.

When I looked at it against a white tissue there was a little yellow to it.........

Sounds like your girl is Preggers to me. She'll be fine no need to worry.

Sounds like she's pregnant, that was always a good sign for my girls and something I kept my eyes open for.

If the color were to change then of course consult your vet but what you're seeing sounds normal for a pregnant bitch :)

Best of luck!

Just want you to be careful.
As far as I know, Baytril is not a low grade antibiotic, in fact, I believe it is pretty strong.
And should not be used on pregnant and nursing bitches.
As always, be sure to check with your vet first.