During this time, it is VERY important to keep your mother hedgehog as calm and happy as possible.
At 28 days from first day of breeding, Clean your hedgehogs' cage VERY well. Sterilize the cage itself, as well as any cage accessories. At this point, it is recommended to switch from a fabric liner if you are using it to a absorbent, odor controlling bedding. Soft shaved pine or aspen works well here. Be aware that it is going to be at least a couple of weeks if not longer before you can do a good cage cleaning again, so make sure it is as long-term doable as possible. I recommend adding an extra deep layer of shavings, 2-3 inches is a good idea.
If you haven't already found a good nest box option that is good for both you and your mom hedgehog, then 28 days is the time that this needs done. Also, provide your mom with a supply of nesting materials. I have tried several different things, including hedgebags, small blankets, etc, and have BY FAR decided that plain old simple toilet paper works the best. Moms will shred the tp and arrange it to line their nesting box, which provides them with a lot of entertainment and destructive outlet. They usually shred it small enough that there is no chance of the infants getting lost in the folds of it, which was a big problem I had with the fabric nesting materials. As well, moms will often remove soiled areas of the tp from the nest box, which can then be removed from the cage and replaced with fresh clean tp. It's cheap, everyone has it, and no one cares if you throw it away. A single roll of toilet paper can last for a LOT of moms. I usually offer about 8-10 sheets of tp for the initial offering, and then add as needed.
You should already have your mom on a good quality diet. At this point in time, make sure that you keep her bowl consistently filled, and keep an eye on her eating habits. Know how much she normally eats, so you can be aware in an instant if she ate less than typical during her normal eating times. Continue to offer her treats, but make extra sure that the ones you offer are super nutritious. Make sure that water is also readily available, and in a container that a baby can NOT be dropped into and drowned.
I recommend removing the wheel at this time, if your mom is a desperate wheel fanatic, and seems stressed out over the lack of wheel, then you can give them some supervised wheeling time each day until the delivery. If she isn't stressed, just leave it out so she can save her energy.
Before the delivery, it is ok to spend some time each day playing with your mom as usual, HOWEVER, if she seems agitated, stressed, or otherwise more uncomfortable with being held than usual, put her back in her cage and give her space. Do not travel with her, expose her to strange people or experiences, or do anything else that can stress her or make her uncomfortable. Be very gentle on her belly, any rough handling can cause her to miscarry or rupture a uterine horn, which can kill her and the babies.
Watch her for signs of pending delivery---- these can include unusual restlessness, irritability, cage destruction, reduced appetite, increased drinking, pacing, or almost any other change in normal behavior. Once you think that delivery is pending, LEAVE THE MOM ALONE. If necessary, add some additional tp for nesting, fill food and water containers, and just leave the cage alone.
Typical gestation is 35-38 days, HOWEVER, you need to prepare for possible delivery anywhere from 30 days from first breeding chance to 50 days from last breeding date. During this time, do NOT disturb anything in the cage without listening for soft squeaks, looking for evidence of blood in the bedding, and listening and watching for the reactions of the mom.
Once you feel that there has been a birth, leave the mom alone. Don't peek at the nest, don't do ANYTHING for the first several days except very quietly take care of food and water issues, and remove any bodies or very messy areas left in the main area of the cage without disturbing the mother. Be prepared that she may not leave the nest much for the first 3-4 days, and then may only make quick runs for food and water in the dark for a while afterwards. The first 2-3 weeks are going to see the mom spending almost all of her time in the nest, and very little time outside of it. The important aspects of your behavior for the first 2 weeks is to give the mom lots of space, and to avoid ANYTHING that can disturb her, whether it is strange noises, voices, smells, or whatever.
If you find a baby outside of the nest area, use a clean spoon (plastic spoons are a handy thing to have around) to carefully pick the baby up and place it back into the nest area. When the mother is in the nest area, do not disturb her. If you see her outside of the nest eating or drinking, you can use a small flashlight and look in through the opening of the nest box, to see if you can see the babies. If she huffs, runs for the nest, or otherwise seems disturbed, close the cage, and leave her alone.
If you have concerns that the mom is not doing her job, give her time. Sometimes it is hard to tell that a mom is taking care of her babies, and hard to tell the difference between careful carrying of the baby and injuring it. If you disturb the mother, she is either going to kill the babies or reject them all, leaving you with a difficult and almost impossible job of handfeeding. Success rate of handfeeding baby hedgehogs is VERY VERY low, and is something to only take on as a very last option. If you have a job, school, or something else that requires you being able to keep any kind of a schedule, then handfeeding is going to be almost impossible for you. Handfeeding infants involves about 2 weeks of feedings every 2 hours around the clock, then a couple of weeks of slightly farther apart feedings. The babies have a much better chance with the mother even if you have concerns about her care. If she is destroying the babies, be aware that there may be a reason for her actions. Mom hedgehogs know instinctively whether one of her infants is ill or has internal birth defects, and will kill that baby to prevent "waste" of nutrients.
Essentially, the main things to remember during this period are to give the mom her space and not stress her in any manner, and to provide plenty of food and water.