Advice needed please

My cat gave birth to three beautiful, healthy kittens around 10am this morning. She had already given birth to 2 of them when we awoke, and pushed out the third shortly after. The first two were still sticky and bloody, so I think she had them pretty close together. After a short while she seemed to be pushing again, so I left her in peace assume she was going to have another kitten, though when I checked half an hour later there were still only three kittens and she had stopped pushing.

On and off all through today she has been licking at her back end but I assumed she was just cleaning herself up. However, I went to check on her a little while ago and I could feel a lump that felt very like a kitten head. I could feel it for about a minute, then I couldn't feel it. About 5 mins later I could feel it again and again I lost it. She has now moved onto her other side and I cannot feel anything that side.

Is it likely there is another kitten in there? I have done some research on the internet and have seen about interrupted labour, but how common is this? She had no problems birthing the first three and they were good enough sizes at 95g, 101g and 114g.

The mom is eating and drinking and the kittens are feeding well. If it is another kitten it is very high up and nowhere near the birth canal. What else is it likely to be?

ANY advice would be very appreciated.

In my experience, they don't eat until they are "done". Could she just have been passing the final placenta?

Again, I will say I had a cat once who gave birth to a stillborn kitten one week after she had given birth to three. (Too premature, they didn't make it)

This was the 1960's - we didn't take her to a vet. But these things can happen.