Sugarplum--miscarriage?

Question
Hi Tamarah,

I don't know if you remember me or my entire story, but Sugarplum bred 21 days ago and a weird chain of events has happened since then.

The first 15 days went fine, but she was very flat, so we came to conclusion she was just having a small litter of one or 2 like her mom. But she is so flat we thought she wasn't pregnant at all at one point. Then, on day 17 she bled out her "lady parts" quite a bit. I read online this means a miscarriage, however the other 2 mice including her own mom bled too and the babies are all grown now. And on top of that, her mom (Sapphire) was very flat too, but her and her brother were born at 21 days perfectly healthy.

Sugarplum is nesting, drinking and eating a lot, plus she's very possessive of her hide-away we gave her in her own aquarium. She's happy as a clam and shows no sign of distress...

We are so confused! Now she has a clear yellowish goo coming out her backside too, which usually means in humans birth is going to occur.

Then yesterday, and this really confused me, someone told me the real gestation is 25 - 28 days, not 18 - 21.

Help!

Thanks,

Lydia & da Plum

P.S.: All our nearby vets, if you get me, are crap and all they'll say if something's slightly wrong with her, "sure, we'll put her down for ya." That's nowhere on our list.

Answer
Hey there,

The gestation period is most certainly 21 days on average.  18 days is a little early but absolutely happens, and in weird cases it can totally be 22 or 23 days.  25-28 could be true for other rodents, but definitely not for pet mice!  Other species of mice do have different gestation periods though, like spiny mice or deer mice, for instance.  Some mice show that they are pregnant, others are barely noticable, and still others may not show any change until one day you wake up and they're tummy is the size of a golf ball!  Just depends on the mouse.  :)

The bleeding and goo might mean babies are on their way, but it could also mean complications (like miscarriage).  There is always a little blood and fluid in birthing, but the mom typically licks it up before you would be able to notice it.  If there is a lot of blood this could mean either that she is not that interested in keeping it clean (which might indicate discomfort or pain), or that there is more discharge than there ought to be.  The other possibility is that if she is still not obviously pregnant (when you gently hold her tail behind her she will try to walk forward, allowing you to briefly glimpse her tummy swell as she stretches before you release it to keep from ouching her), she could be having an unrelated problem that needs medication.

What I actually think is the most likely to be occurring, especially since you say her relatives have had the same problem, is that part of the litter is not surviving to term and is being miscarried.  Unlike humans, mouse fetuses grow separately in the uterus, and some may make it while others don't.  When a mouse fetus dies before a certain age it may be able to be reabsorbed, but other times it's too big and needs to be expelled to keep from decomposing inside and hurting the mom or the other pups.  In this sense, it would a very good thing she is bleeding before birthing!  So, what I think is probably happening is that some of the pups inherit a bad combo of genes (there are certain lethal genes which can keep them from maturing when they inherit two copies), but the remaining pups are fine and are born normally.  This makes it seem like they are just having smaller litters, but really, only part of the litter is healthy and robust.  If I were in your shoes I would expect a healthy, albeit smaller litter in the next few days, but I would keep a very close eye on her just in case.  Watch out for a lower appetite or water intake, panting, laying out flat and not responding as well, or a messy rear end that could mean she isn't grooming properly or that something else is wrong.  As long as she appears comfortable and happy, I wouldn't worry about taking her to the vet (esp if he's just going to tell you to put her down!  How rude!).  Hopefully all goes normally and your litter will be here soon!  In the future, though, I wouldn't risk breeding anyone from her family, including the offspring, as they are almost certainly carrying whatever gene may be causing the problem.

Best of luck, and I hope she has some good, healthy squeakers!  :)
-Tam