Can NK cell issues develop after previous live birth?

[Eggling]

Despite my extremely extensive googling I can't find an answer to this so wondering if anyone can help?

I am 33 with PCOS, DH 32 with some iffy sperm results - initially 1% morphology which has more recently been 4%, but now what was highly motility is low (22% progressive motility last sample in summer). We have DD, 2.5, very fortunately conceived our first round of ICSI after 6 failed clomid cycles.

Since May last year we have had 2 failed FETs, a round producing only one day three embryo (shocker with PCOS and my previous round which resulted in 21 eggs, 4 high quality blasts). That led to a miscarriage in feb/ March. Then various cancelled cycle issues over the summer, finally another round of ICSI where I had loads of follicles but only 12 eggs collected, 7 mature, 1(!!) fertilised. Again this made a high quality day three embryo, again I have just miscarried at around 7 weeks.

Waiting for follow up with the clinic but we have already had all the tests they do for recurrent loss. I'm with Create who don't seem to believe in reproductive immunology much, and they seem very focussed on the fact we have DD meaning there can't be an issue with me.

So I guess two questions:

1. Can NK cell issues develop after a previous successful pregnancy or is there no way that could be our issue? In case it's relevant I did develop pre eclampsia just before DD was born.

1. Should we seek reproductive immunology tests elsewhere? Move clinics? I really don't want to do this as is know and like the staff and clinic so we'll by this point, but I'm absolutely desperate.

@Eggling sorry to hear about your losses. I am also with Create. I am not sure about NK Cells but I have recently had recurrent miscarriage tests which showed I had high thyroid antibodies which is an immunity condition, so will be on steroids for my 1st transfer hopefully next month.

Have you had the Recurrent Miscarriage tests? They are 6 blood tests and cost and could be worth doing if you haven't

Thanks @Sunflower360 yes I've had the tests, nothing showed up except slightly low vitamin d which we've supplemented for since. Had kareotyping tests too for both DH and I, again all normal.

I just feel we must be missing something! Don't want to plough on if it will be another loss but equally don't want to waste time and money on unnecessary test and treatments

I thought immunology could be my problem as well as I had 3 miscarriages then two failed IVF transfers after my first child (conceived quickly and no problems). Clinic always thought was unlikely to be immunology as I had a straight forward pregnancy, baby wasn't small or anything and that it was much more likely to be my age (40) and therefore egg quality and I just needed to find that better quality egg. For me I think they were right as I am now 20 weeks pregnant.x

When I was looking in to it there were London clinics doing it (my clinic did offer some themselves too) but they were very expensive tests in London.
If my FET hadn't worked I was going to do some of the tests my clinic offered though as I just couldn't understand why it wasn't working for us.