I noticed a thick, sometimes sticky, dark brown mucous discharge from my girl on Friday night. She'd been bred a month ago so I took her to my vet for an exam Saturday morning. He checked the discharge for abnormal cells/bacteria and said the results were normal, then did a quick puppy check and found at least four via ultrasound. Sunday and Monday there was no discharge but I got up this morning and there was another long string of brown mucous on the floor. Has anyone else ever experienced this? The last time I had a brown discharge from one of my girls it turned out to be pyo so this whole thing is very disconcerting to me.

BTW, there's no foul odor and she's eating and acting normal. If only the darn discharge would disappear I'd be thrilled!

If a placenta is over the birth canal as the uterus grows the placenta will pull away a bit causing some bleeding. It does not sound bad if it is mixed with discharge.
That's the only thing I now of from personal experience.

Congratulations on your girl's pregnancy!
This topic has come up many times, and most often there is no concern for your bitch or the puppies.
A pyometra discharge has a foul odor--it is full of white blood cells and bacteria. It is usually a cream-colored discharge, can be tinged with degraded blood (brown color). I understand, once you have had that experience in a bitch, you get upset with discharges! A pyometra is a true emergency, and needs to be seen by a veterinarian right away.
A mucousy discharge, clear, blood tinged, or brownish (degraded blood from further up the reproductive tract) that does not smell bad, sometimes appears with pregnancy, as it did with your girl, and is normal.
Good that you had her checked out though to make sure...now you have confirmed pregnancy and know that everything is okay!
I had a bitch who showed bright red spots of blood in the snow when she was about 4 weeks along. Did I freak out and take her in for an ultrasound? You betcha!
All was normal on ultrasound, and she went on to have 13 puppies (all survived)! So maybe it will be a good omen for you, too!

Thanks for your responses. I'm breathing a lot easier tonight! I really hope she doesn't have 13 puppies though, lol. That would take a toll on both of us!

Tell me about it! I remember going crazy supplement-feeding half of the litter at each feeding. And I'm older now, definitely do NOT want 13 either!