You're pretty exhausted. The last eleven months have been tiring enough, what with Fluttershy's mood swings, Discord breathing down your neck—at times, literally, it was fucking weird—and you having to man up and actually provide, be a decent partner and stuff. When you heard about the wonders of horse poon, you weren't expecting this much work to be involved.
You're sitting in a labour room right now, which is fitting because you've just undergone nearly a year of hard labour while Fluttershy got to relax and carry your baby. It's only fair that you should be allowed a brief respite, you reckon. Well, very brief and in short bursts, because Fluttershy won't stop screaming. You've tried consoling her, you've tried keeping quiet, and you've even tried those sensual neck kisses that always get her going. Apparently, she's really not in the mood right now. You've got the fresh hoof sized mark on your cheek to prove it.
So Fluttershy's moody as hell. Honestly, you'd think she'd be happy to finally have this baby out of her. Or not. You know absolutely nothing about equine biology—aside from what goes where—and as such have no clue what's got her in such a state, but frankly it's pretty unbecoming. If Fluttershy had been like this when you had met her, you probably would have never graced her with your child.
...Okay, you probably would have. The mare's hot. Less hot when she's screaming, but eh, you'd still bang her. Looking to the dull, pale yellow wall, you begin to wonder whether having a child will impact on your sexual activity. You've come to terms with the fact that it's all you really care about, so you don't feel guilty for thinking about it now. Besides, you've only had like three hours sleep since arriving here, your mind is bound to wander sometimes.
Fluttershy, on the other hand, has had none. You could believe that, because her screaming and complaining has been the main thing keeping you awake, plus she keeps reminding you that she's exhausted. She really can be selfish sometimes.
You aren't paying much attention to Fluttershy's problems, so you begin noticing other things, because you're ultra perceptive. You notice that the yellow on the walls isn't as nice as Fluttershy's coat, you notice that unlike most patients you've been given a private room, and above all you notice the dirty looks that the hospital staff keep giving you when they come in to check on Fluttershy. In particular, Nurse Redheart seems to have an issue with you.
You know why, of course. Back when you had to visit the hospital for banging too much, you had asked the good nurse to give you a nerve receptor test—some genius shit you thought up on the fly—before pointing at your junk, waggling your eyebrows and asking for some 'stimuli'. Obviously, once she had finished with the act, she had found out that you were banging Fluttershy, and quickly became jealous. (Because she totally went for it. That's the version of the story we're going with here, at least.)
Anyways, Redheart keeps mad dogging you, and it's starting to get on your nerves. Does she not realise how much stress you're under? If anything, those nurses should be coming in to check on you. Between Fluttershy trying to imitate the fox's mating call and Redheart being a passive aggressive bitch, you've had enough. You get up and leave your bed without explaining to Fluttershy where you're going. She doesn't seem to care anyway, she's too busy panting and weeping to say anything interesting.
You follow Redheart out of the room and into the corridor. Worst case scenario, you get a distraction from Fluttershy for a little while. Best case, you get her to stop giving you a hard time, and possibly a make up fuck for good measure. You never know, right? Her brow furrows as you approach her, she bares her teeth like a fluffy wolf and gives you the mother of all judgmental stares. Maybe you shouldn't have came on so strongly last time you saw her.
Still, despite your annoyance you're a calm and amicable guy, so you put on your best smile. "Hey, Redheart, what's the matter? You seem a little frustrated. Long shifts lately?" Classic, deflect the issue by alluding to something else that might be annoying her. Mares love to complain about their lives, after all.
Little success, apparently. She actually pins you up against a wall in broad sight, not that anypony walking by comments. This is either about to get sexy or violent, and you're in the mood for either right now. Maybe both.
"You're what's the matter," she spits, staring up at you like a rabid animal, "Do you even realise what you've done?"
"Huh?" As far as you're concerned, you've been perfectly well behaved since arriving. You only brought four beers into the building, and you've only had two wheelchair races with Pinkie Pie. You tell her just that.
Her face only darkens. Apparently, that wasn't what she was referring to, because now she looks slightly angrier, if that's possible. "What you've done is impregnate a mare. Do you not see the issue in that?"
You don't. You knocked up Fluttershy, you're gonna have a kid. So what? "I mean, I'll pay child support, so what's the problem?"
"You mean you aren't even planning to stay with her?" Redheart's voice became shrill and sharp, you're clearly digging your own grave here. "You really are despicable."
"Look, I don't need your shit right now. I'm tired as hell and Fluttershy has been nonstop bitching all day, so if you could get to the point?"
"How do you think having a foal with a pony mare is going to work?" she asks, her curiosity apparently genuine.
"Well, apparently it takes eleven months instead of nine, but I'm guessing eventually she'll stop screaming and it'll pop out?"
Redheart looks like she's about to have an aneurysm, she's literally shaking with anger, a hoof either side of you as she keeps you pinned against the wall.
"...So, not that simple?"
"Not even close," she grunts out, "and the fact you allowed this to happen, that the pair of you allowed this to happen without knowing what the result would be is appalling. We don't even know what will come of this, it's never happened before. Your chromosomes are dissimilar, you're of two completely separate species—"
"Ohh... Oh. Oh." Come to think of it, you hadn't considered that. Probably should've given that one a bit of thought, in hindsight.
"Do you see how serious of an issue this could be?"
You scratch your chin for a moment before feeling a spark of realisation. It was simple. "Doesn't that just mean the kid will be a centaur?" There, easy solution. There was a reason Redheart was a nurse and not a doctor.
"That's not how it works," Redheart deadpanned, looking wholly unimpressed.
"How do you know? It might work like that. You just said it's never happened before."
"Centaurs aren't a hybrid species. Well, they are, but they've always been that way, same as griffons. It's just how they evolved over time."
"...So you're telling me that griffons weren't made by—"
Redheart cocked her head. "By what? A lion fucking an eagle?" You almost feel her eyebrows straighten. "Shockingly, no."
You pause and reevaluate your entire understanding of griffons. Doing so lends credence to what Redheart is trying to tell you. You don't like entertaining the idea, but it's beginning to make more sense. "So you're telling me that centaurs weren't made from humans and horses screwing either?"
"How many times have you been told that you're the first human to be here in recorded history? Don't ask stupid questions."
It's true, you did hear that a lot. Come to think of it, this conversation begged the question of how the hell a chimera was made. "So what does that all mean?"
"It means you're a freaking idiot." Redheart squares up to you, arching her back to gain a few inches, though it barely brings her to your chest. Still, you can feel her breath on you from there, and as much as you're afraid it might compromise your manliness to admit so, she is pretty imposing. "You just couldn't help yourself, could you? It's bad enough that you go around acting like a lecherous, chauvinistic brute all the time, but the ponies here have actually managed to tolerate that, we can accept that you're different. What I can't abide by is your choice to bring a child into this world without a shred of thought about its health or wellbeing. Both you and Fluttershy have brought this upon yourselves."
You're beginning to feel more and more cornered. You don't know whether to cry and beg her to stop berating you or headbutt her and run. Both sound equally cowardly, and you're torn between which would work out best for you in the long run. Still, you're being chewed out for something you didn't even realise was an issue, where's the fairness in that? "What would you suggest I had done then? It isn't like I asked her to get pregnant, it just happened, you know?"
Redheart sighs. "Have you ever heard of a condom?"
"Uhh, should I have? Didn't think to check if they existed here."
"You're repulsive, you know that? You go around sticking your dick in anything that moves and you haven't even taken the time to educate yourself on safety measures. What's wrong with you? You've had eleven months of alarm bells going off, how did nothing make you think to yourself 'oh wait, this might have been a mistake?'. The fact that you're so nonchalant about this is what really gets to me, it's like it doesn't even affect you."
You consider this. It's not like it's your health that's affected by this, you'll still be good to go no matter what. Then again, Fluttershy would be disappointed if the kid looks funny. "So, what's gonna happen?"
"We have no clue," Redheart's eyes met the floor, "Fluttershy is dilating slower than average, and the foal is overweight. Unfortunately, we have to face the prospect that this child might be born with severe deformities, should they survive the birth at all. That isn't even considering the question of their mental health, disability is a major concern. Do you understand the result of your actions yet?"
Your face straightens, you can't believe your idiocy. "Yeah, I do."
Redheart's features soften somewhat. "I know it doesn't change anything, but it's nice to know that you at least realise what you've done. Maybe it'll help you to support Fluttershy through it, and—"
Your rising panic cuts her off. "If Fluttershy gives birth to a deformed child, nopony's ever gonna want to screw me again! Th-they'll all be scared that I'll do that to them! This is serious shit..."
Before you can say 'last minute abortion' a small flurry of very real, very heavy blows rains down on your stomach and thighs. You clutch your stomach as you sink to the floor, a seething Redheart standing over you. "I am going to allow you to be present at the birth for Fluttershy's sake. If it were up to me, you would already be gone. Once this is over with, you are not to come back here. I don't care if you break both of your legs and crawl all the way here, I will not treat you. Is that clear?"
You cough up a little bit of blood. It's a good thing too, because it cut you off from saying 'what about my third leg' in response. That probably wouldn't have gone down well. Simply nodding, she turns and storms off, leaving you to lick your wounds and prepare for the birthing.
You consider asking Twilight if she would be interested in studying your offspring, it sounds like her kind of thing. If not, maybe she'll be interested in examining your seed instead. No matter what, you know one thing for a fact, and the thought alone puts a smile on your face. You're gonna have a species named after you.
Hours of seemingly unnecessary screaming later, it was apparently time. You have to admit, you're strangely interested in what the result might be. You thought about making bets with the hospital staff on how many hooves it would have, whether or not it would have feet, and things like that, but decided that might be a little tactless. You arenn't a monster, after all. As such, you conclude to keep your guessing to yourself.
Fluttershy asks to hold your hand. She usually only did that in front of her friends when she was trying to make a statement or make them jealous. Not seeing why not, you oblige, only for her to sadistically crush the thing against the side of the bed railing as if it was sadism Tuesday. You arenn't too impressed by that, so you call her a stupid bitch and decide to wait outside. Besides, apparently the thing was crowning, and that meant that with the size of it, it was basically trying to rip her apart from the inside. You aren't a squeamish guy, but you draw the line at watching that, so you decide to sit in the lobby and screw around on a wheelchair. Unfortunately, Pinkie isn't around.
Just as you began to drift off, Redheart stands before you, prodding you awake. Prodding your fresh bruises, no less. Maybe it was sadism Tuesday after all. Brushing off your grogginess, resisting the urge to tell her to fuck off and let you sleep, you notice the expression on her face. You're very analytical, after all, and can read ponies like a book, so seeing exactly what she was thinking isn't so difficult for you. She looks mightily pissed off, but not so worried. That piques your interest, you could swear she was really scared earlier.
Clearing her throat, she gestures to the double doors she emerged from with a hoof. "I-it's done now, would you like to come through?"
That was clearly a rhetorical question. You rise to your feet, starting to walk out of the room behind Redheart. You knew you'd see for yourself in a few seconds, but you're curious, so you decide there's no harm in asking. "Sooo, what's the damage? We talking a total vegetable here, or the elephant man reborn?"
Redheart spins on the spot, facing you with a glare. "Excuse me?" she barks, fire in her eyes, "Have you no tact whatsoever? Honestly, for a human being you have absolutely no humanity."
How scarring. "Are you going to tell me what happened, then?"
Redheart shifts on her hooves before beginning to walk again, facing ahead. "You'll be pleased to hear that the colt is healthy. At least, I think you will be."
You choose to ignore the part of your mind that was quietly hoping for something truly obscene to be waiting for you on the other side. That part of your mind is really weird and you shouldn't indulge it. Still, something about this strikes you as odd. "Well, if that's the case, why do you still seem so pissed? I thought you'd be relieved."
"...Just come through."
So you do just that. You continue to follow Redheart through the doors, down the corridor, and eventually into the room where Fluttershy lays—looking half sedated—with a large bundle of sheets wrapped in her arms.
You feel something surge in your chest. Maybe it's paternal instinct, maybe it's a shred of selfish emotion. Maybe it's just curiosity. You push past Redheart, moving yourself over to Fluttershy, planting a small kiss on her forehead as a thank you for finally being quiet, then allow your eyes to shift and settle upon the small face poking out from the sheets.
You stare and you stare, and eventually pull back the sheets, exposing the colt's entire body. Thankfully, they'd washed the blood and shit off of him already. As you take in his visage, a large grin settles across your face, you've never felt so proud.
You look to Fluttershy, your heart filled with warmth, your lips quivering as you try to form the words. "He's... He's a—"
"A centaur, sweetheart," she replied, her voice hoarse. "We did it."
"We did it! I fucking did it!" Wheeling around, he pointed a finger at Redheart. "In your fucking face! You told me I was sooo stupid for thinking we'd have a centaur, and you were wrong! I was right, and you were wrong! This is the happiest day of my life!"
Redheart stands shaking her head at you in disbelief, you don't care. Today, you have proven something. Not only was your seed strong, stronger than any man's seed reasonably should be, but you have also made an important historical discovery, one that will transcend the ages and remain long after you pass on.
At some point in history, man had visited Equestria. When they were there, they had found horses. They had then fucked them, and that is how the centaur was made. Your creation proved that beyond doubt, it had to be what had happened.
The discovery left you with mixed feelings. One way to see it was that it meant your arrival in Equestria wasn't special anymore, you were no longer unique. Another, better way to see it was that not only were you not the first human to fuck a pony, which makes you feel a lot more secure, you've also solved the conception of the centaur, and in doing so confirmed that there was a distinct possibility that there exists a permanent way for humans to come to and from Equestria.
This meant that there was a chance you could see your world again, see your people again. There was even a chance that you could travel between your worlds at will, should you find the means, and that ponies and humans could foster relations, and learn and grow together.
Looking at your boy, you feel a surge of self-pride. In Fluttershy's arms there laid the birth of an utterly staggering discovery, and you were at the centaur of it all.