I purchased three females and one male sugar glider a year ago from someone near me. I was wanting them for breeding aswell as pets but as soon as I got them I noticed something was wrong. Two of the females had a baby in their pouch that looked like it was almost ready to come out, but they didn't seem alive, they wernt moving and almost felt hard. I assumed they were dead since they wernt growing at all over a period and within the next few weeks I noticed that both of the females had either eaten or gotten them out of their pouch somehow. They haven't had any babies within the last year but one surprisingly is pregnant and the baby is looking decently healthy.

I was just wanting to know what I could do to make sure what has been happening doesn't continue and what the cause of their babies not doing so well might be.

Thank you.

I would start by reading some information from the websites available.
then think about getting a book or two or three that might have better information.
many books cover care and also have parts on breeding.
facebook has some groups I hear ( I'm not on facebook)

I have my hands full with care and food and playtime, breeding just
seems to much for me, you may also need a license to breed and sell legally.
I have read that many gliders do not have successful first pregnancies,
and a stressful environment, move, new cage, bad food diet can cause lots of
problems.

not trying to be mean, but I feel that someone should take about 3 years or more
having gliders, caring for them, learning there behavior and how to bond to gliders
before moving into breeding. these little guys are NOT cats or dogs. they are
different and it takes time to figure that out as well as bond with them so you
can have a close and trusting relationship during breeding times.

There could be many reasons it happened.

Age, first time parent, Inadequate diet, poor housing conditions, stress, cagemate issues, inbreeding, something was wrong with the babies, breeding with a colony of 3 females and 1 male not working, low milk production or mastitis etc... There are lots of reasons it can happen.

The only sure fire way to prevent it is neuter the male, and I'd suggest that if it happens again because at that point they just might not want to be parents or they could be to closely related producing unhealthy babies.

If you still want to breed then find a reputable breeder that has lineaged gliders for breeding to help increase the chances of healthy babies.

If it's just the one that's pregnant you could separate her and the male from the other 2 females n see if that reduces the moms stress level and risk of the other 2 females harming the babies.

There aren't any books specifically about breeding to my knowledge but Suz's site has a lot of info on it from breeding to rejected babies https://www.suzsugargliders.com/breedingsugargliders.htm and there is a group on facebook specifically for breeding for people with all levels of experience https://www.facebook.com/groups/breeding101/