No, a D&C should never be a 'matter of course': it carries its own risks and those need to be weighed up against the risks of the issue.

In my case, I was offered a number of options for the retained placenta (mine was still attached and was being 'fed' by blood vessels...it was super weird and i felt like i was inhabited by aliens lol): I could have a D&C, I could continue with the antibiotics and wait a week or two and see it had resolved.

I decided to wait it out (this was after the PPH...i was at this stage about 8 weeks PP). after a long discussion with a private OB (we decided to seek a second opinion from the public system as i felt they were not in a position to give me detailed information or support and my independent midwife agreed with me), we felt that it was now small enough to wait and see for a couple of weeks and hope that it would resolve, and if it didnt to then finally make the call to have the D&C.

Why did i choose this route? I had been on a great deal of ABs at this stage. and they were doing a number on myself and my new baby (we BF), i was super keen to get off them ASAP. I was informed by the OB that no matter what, after a D&C i would need yet another course of ABs. (I was up to my 5th). For me, I chose to wait and see, to reduce the chances of another round, and also to try to pass it naturally and not risk my reproductive health unnecessarily (with a procedure that might not be needed) and to reduce my contact with hardcore ABs. i had come to the conclusion that if after those extra 2 weeks i was still cactus and not passing the placenta that, for me, the risks were too great to not intervene further, and agree to the D&C.

I was happy with my decision, and the OB was also happier. he did offer to give me a D&C on the spot if I liked, but after i had made my decision, he told me that he too, felt it was the better option.

I would think that what you would need to do is to probably organise another scan and check that it has all passed. are you in contact with this issue with the hospital or midwife that you birthed with? This would still fall under their jurisdiction (retained placenta) and might be worth following it up with them.