At 35+ weeks pregnant with my 4th baby I decided to try a Birthing Ball as I have been in a lot of discomfort down below with pain and crazy amounts of pressure I hadn't experienced with my previous pregnancy's and had read that it can help if you sit on the ball.
There seems to be a lot of benefits to using one that I never knew about I actually thought they were only used while in actual labour from what I had seen of them on tele but apparently not as I found out some really useful information about using it in the later stages of pregnancy.
A birth ball is great for the last weeks of pregnancy just for sitting on to relax, watch tele or at the computer and will be easier to get up than from the sofa for example. It can also give you a little workout for your tummy and back muscles if you sit and gently bounce or rock on it, it will also improve your posture and balance. you can also try doing your pelvic floor exercises whilst sitting on it. If your baby is back to back using the ball can help to move them and get them in the right position for birth, sitting on the ball leaning slightly forwards so your knees are lower than your hips can help your baby to swing round. Using this position on the ball can also help to relieve backache.
There isnt apparently much difference between a birthing ball and a gym ball either the one thing to check though is the size as they are made for certain height ranges for example the 55cm one is most suited for people up to 5ft 4. It should tell you this information in the product details if you are buying online or if in store then ask one of the staff members.
I bought mine from Argos it is a 55cm Argos Value Range Gym Ball £4.89 it comes with a pump included and is great for such a low price some of the reviews said the pump was rubbish but we had no problem with it. I have only had it for a couple of days but I am finding it very useful and comfortable, it such a relief to sit on it when the pressure is too much. The kids love it as well they keep running off with it and bouncing it around the house. Will also be great for exercising after I have given birth, a good investment I think.