Again, I'm so grateful for all your thoughts. I will be talking to DS on Facetime this weekend. I know all I can do is sympathise and offer a listening ear. I remember my late mother's brutal tendency to say what she was thinking, honesty being the best policy in her mind, and I am so anxious not to blurt out something that would be incredibly hurtful and inappropriate.
I won't say, don't worry, they can't stop worrying. I won't say, it doesn't matter, because right now it matters very much, to them. I have thought, but won't say, is there a reason for everything? No, I don't buy that. And we are not religious (neither are DIL's family) so I'm not putting it in the hands of some imagined higher power. I have thought, but won't say, perhaps it's for the best, perhaps the repeated failure of implanted embryos to stay put indicates there would be problems down the line if the pregnancy did continue - a later miscarriage would surely be more devastating than a failed implantation. Of course I won't use the word 'fail' - the procedure might have failed but the last thing I want is for DS and DIL to feel that either one of them is failing. I can't think of anything they WOULD like me to say, other than that I love them no matter what. But love doesn't make it better.
Gagajo thank you for mentioning your experience with medical treatment, it's reassuring. DS has had minor surgery once or twice there without problems, but he has commented on a perception that you might be expected to 'pay under table', and that's an uncomfortable thought. Generally he has not encountered hostility at all and he loves the country, only DIL's former employer was very vocally and unpleasantly opposed to her involvement with a foreigner and that did shock them both. He is polite, respectful and kind, not given to rubbing people up the wrong way, so I will discount that nagging question.