Mice become fertlie 28 days after they are born. Some have been known to breed a little earlier at 21 days, however that is a rare case. The pregnancy term can last 18 to 21 days. At 14 days in the pregnancy you should be able to notice a very round mouse or your mouse has become "pear shaped".

First of all if there was a male in the tank he needs to be taken out. Mice can get pregnant right after giving birth and that is very stressful for the mouse. If there are other mice that are female in the tank (meaning 1 to 3 mice) then it is personal choice wheter you leave the mice in the tank with the pregnant one or not. Some mice may see the cage mates as a threat and that can cause them to abandon the litter or consume them. Other problems may arise in that one of the nannies will try to steal the babies. But other than that usually the nanny system works well.

The mother mouse needs to be on a special diet. She needs the food that you are already feeding her along with fruits and veggies (not leafy greens) in small amounts, as well as protein. Some people prefer other foods for the protein than what I mention but this is based on my personal preference. A little bit of kitten food or half a milkbone (brand) milkbone a day. Remember to feed them the protein in small amounts though because too much of a good thing can be bad. I like using these foods because they foods cannot rot in the cage with the mice. Always mmake sure they have plenty of food and water.

For housing it is good to make sure the cage is in a low activity room so there won't be any disturbances. The tank should provide good ventialtion. An aquarium will work best as the babies can squeeze through the bars. A well ventilated next box is a good idea too. Give them the reg. bedding and nesting material such as paper towels toiet paper, etc. When a mother mouse is about to give birth her behavior may be a little different. Mice are normally great mothers, however there is always a chance that the litter won't make it. If you notice your mouse eating a baby this is normal. In mother nature it is the mother's duty to see that her babies are strong for survival reasons, They can smell defects in their babies, sometimes just one of the babies will be sick and sometimes all or none will be sick.

After the mother gives birth leave her alone for a few days. If she really trusts you then you can have a peek at the litter in 3 days. Wait for the mom to leave the house then pick her up and place her somewhere outside of the cage. Rub your hands in the bedding to smell more mouse like before handling the litter. If the nest is bothered too much then it can cause them to consume the entire litter because the mother will think it's an unsafe enviroment.

The cage should be cleaned after the first week. Mice will hit a flea stage when they are a couple of weeks old. This is where they jump at random times and can jump out of your hand so it is wise to grab the gently by the base of their tail then support their body immediately with the other hand. The mice will need to be sexed and seperated by 21 days at the earliest, 28 days at the latest. I personally separate mine at 24-25 days. If there is anyting I did not mention or you have another question feel frre to pm me (Mousey) or ask it in the mice and rat discussion for a quicker reply.