Er, question my apparent ignorance, but seeing
1) childbirth is one of the most painful experiences that doesn't instigate a state of shock, so drugs that control pain seem a good idea
2) aren't hospitals employers of those painfully reclusive people who investigate the effects of drugs, (I think they're called pharmacologist!(
3) it's far from the first time such a thing has happened *Angela Rippon had her case highlighted by 'Top Gear' (I'd love to say that was a well thought out play on words), so who are te fucking megaminds who didn't correlate bagels with positive tests?
And as a final comment, never been tempted to buy some pungent drugs, leave them behind say a radiator, then contact social services and explain you don't feel comfortable leaving your child with their grandparents who's house always seems to be full of dodgy druggies. Of course, the case wouldn't reach the courts, but once all the hoo-ha has died down, initiate a conversation, full of faux sympathies, explaining that you also have been the victim of some sack of shit telling lies to social services (implying you have no idea which sick twat would lie about such a thing), with a final, "they seem to think there is no smoke without fire" and that it would have been so much more serious if they had found a sizeable stash of drugs (if needs be).
Hell, you said she hates you, so what have you got to lose, short of xmas/birthday cards with thinly veiled contempt. Best to do it at a big family gathering (if you can do it without grinning like a village idiot, while sympathising with the ordeal she has just suffered.
A "anything you can do, I can do in a much more coordinated and vindictive way" hinting you'd be willing to give up every treat in your life, for months if needed, if she didn't just fuck off, in order to insure they found a shitload of drugs.
My wife's younger sister, who has Hyacinth Bucket tendancies and sometimes made frankly quite insulting comments about my wife (well g/f at the time) mental health. I knew how she could really put the boot in, by getting married in a 13th century castle, with OTT snobbery. Knowing my wife had spent her life not letting such comments really upset her, I decided I'd rather just spend £12k on a second hand car, rather than twice as much on a snobmobile. I never got upset when we visited, but when I told her, on our honeymoon, she pissed herself laughing at a dish served cold (revenge); smoked salmon, in this case!
I may look like a bit of a simple hippie, but I explained, hurt her, in any way, and I'd take it like it had been a personal attack on me. Fuck with my family and I WILL take it personally, even from In Laws... (my little sister later told my wife that I had been practicing being a twat from her earliest memories. I can make my sister's life a pain, when we were little, but any other fucker try it and I'd find a way to make their lives a misery - this was back when I had two hands and somewhat lacked finesse, choosing instead to just hit them with a piece of wood, or kick the back of their knees as hard as I could, while on a concrete floor.