Pregnant rat

Question
My rat got pregnant about 2 weeks ago. She developed a lump under her left arm a few days ago, and now she has some bleeding. I can't imagine the two are linked somehow, but through all the reading I've done, this bleeding is what happens right before they have their babies. We're uncertain of what's going on, but we're kind of worried.

Answer
Do you know the timeline for fact, or is it your best guess? A rat's gestation is about 21/22 days, so if you know for certain she's only 14 to 16 days into her pregnancy, premature bleeding is usually a sign of a miscarriage, absorption or premature labor, all of which are bad indicators for the litter itself but may not be a problem for the doe (note I said may; things can always go wrong, and I recommend keeping a very close eye on her). If you're off a week or uncertain on the date - it may just be a normal labor and nothing to worry about at all.

The tumor is probably mammary and those are usually estrogen fueled, meaning it's most likely not cancerous or painful (and won't be painful until it's big enough to rub the cage bottom) - nor is it related to her pregnancy necessarily, other than the hormone spike while she was pregnant may have had something to do with the sudden growth. When you can (likely after the babies wean), you can have it removed and probably extend her life considerably. Tumors are always easier to remove while they're "new".

Good luck!