I am getting ready to machine quilt my baby quilt. Just wondering if Polyester thread would work ok or if I should use cotton covered thread. I will quilt in the ditch so it doesn't need to show.

I always use cotton thread

I would suggest that you always use a thread type that matches the fabric. If a cotton quilt use cotton thread. That will insure the pressure on the fibers is the same and not to tight or too loose etc.

It is cotton fabric. Should I use quilting thread? I thought it would probably show more since it is heavier. And I don't really want it to show.

If you don't really want it to show , I suggest an invisable thread.

Do NOT use hand quilting thread in a machine. The coating/glaze/wax will gunk up the tension disks and other mechanisms. You can tell it's glazed even if not labeled, by the coil it will have coming off the spool. You CAN use poly thread on a cotton quilt. There are many thread lines by celebrity quilters which are poly. So pick something that will have the look you want on the back, won't show your flubs on the front, and won't give you grief in the machine.

and do not use invisible thread on a baby quilt. too much chance of missing long tails and baby getting them wraped around fingers.

Oh thanks so much. I did consider invisible thread but decided against it. Glad I did now. And you are right about hand quilting thread. I does have a coating. I hadn't thought about that. I think I will stick with polyester thread. Since it is thinner I think it wouldn't show as much.