Mouse grew but hasnt given birth

Question
QUESTION: I got 2 mice as a breeder project a month ago. The girl lived with the boy for about 3 weeks, until I moved her to her own cage in hopes of babies. She's been pretty chubby for the last week or so, and yesterday appeared to be having contractions. She would kind of stretch her body out, pushing back with her hind legs. Today, however, she's not having either contractions or babies.

So, 5 days before she's in heat, 2 days for coitus, and 21 days for pregnancy means she's 3 days overdue, at least. There's no prebirth or blood, and she doesn't have a baby stuck. Should I just be more patient, or is something wrong?

ANSWER: Dear Jay,

The mice might not have mated right away.  Not every boy mouse is completely savvy about mating the first time.

It's hard to know what you would call 'pretty chubby,'  but a three-week pregnant mouse is HUGE.  She looks like a pear.  'Pretty chubby' might mean two weeks.

I suggest waiting to see what happens.  If she is going to lose the babies (spontaneous abortion) there is nothing you can do.  It would mean there is something wrong with them.  Her body would naturally destroy them.

Chances are you will have babies within a week.

squeaks n giggles,

Natasha

---------- FOLLOW-UP ----------


Preggers?   QUESTION: Hi Natasha,

Here we are a week later babyless. The attached photo was taken 5 days ago, with today being +37 days after they were first cohabitated. She looks about the same size right now, which is still much longer and fatter than her original. Perhaps I bought her young, pregnancy never happened, and she just had a growth spurt? She's been housed alone for the last two weeks, after 23 days with the boy, so she must be nonpregnant or about to give birth...What do you think?

Also, her nipples aren't prominent so I'm leaning towards not pregnant, but I really don't know.

Thanks

Answer
Dear Jay,

If she hasn't gotten a lot fatter in the six days since you first wrote, then she definitely isn't pregnant.  I can't tell the shape of the mouse from the photo as she's sitting, but her full size looks like it could be normal--  for an adult mouse.  She definitely doesn't look like she was a baby any short time ago.  

There are some other, more unfortunate possibilities that have to be taken into consideration.  She could have an internal tumor.  Tumors grow relatively quickly in mice.  They often don't interrupt the mouse's normal function until they become too cumbersome for the mouse to proceed with its daily activities, though a tumor in the abdominal cavity could press into internal organs.  Another main possibility is some kind of infection. She could have some kind of infection inside which produces an abscess.  This would likely be visible in that she would be a little lopsided.  A third possibility is some kind of internal blockage.  This would definitely result in some kind of changed behavior, such as eating less and acting sluggish.  Any of these would also explain not getting pregnant.

The only way to make sure she is healthy is to take her to a vet, who will palpate her and have a far better idea of what is going on.  If she has an infection she can have antibiotics.  

Hopefully she is just a fat mouse.  Some mice are just fat.  I once bought a 'pregnant' mouse from the pet store, intending to have the babies, and she just stayed very fat.  Another mouse of mine grew so fat that, worried about an internal tumor, I had her X-rayed.  Again, she was just fat.  As long as you are feeding the mice a balanced diet low in fats and with no sugar, fat mice are perfectly healthy.

I wish her luck!

squeaks,

Natasha