Title: The 17th
Rating: PG-13
Pairing: John/Sherlock
Wordcount: ~2,300
Warnings: omegaverse, mpreg
Disclaimer: I do not own Sherlock, and I do not make any money from this fanwork.
Summary: The 17th comes and goes. Sherlock misses John's monthly heat. So does John: Sherlock doesn't take it well at first.

John's monthly heat isn't too bad. He experiences the symptoms with precise regularity on the 17th of every month, nearly without fail since he returned home from Afghanistan. His cycle was completely inhibited during his tours, but extended use of a heat suppressant has negative long-term effects, including sterility. John was somewhat relieved that his cycle returned to normal in just two months after he switched from the heat suppressant medication to the more mild contraceptive: he still experienced heat symptoms, but without the chance of conception.

Even his heat symptoms aren't so bad. Some omegas are hit hard, able to do nothing but shut themselves away for the duration. Some go crazy with it, pouring out a pheromone that attracts unattached alphas in a mile-wide radius. Some omegas become ridiculously suggestible, gullible.

All omegas experience some variety of the symptoms: increased libido, increased pheromone output, increased receptivity - but John is fortunate to experience these to a much milder degree than most. Still noticeable, of course: he knows the moment his heat begins, because his blood starts to warm, his skin starts to itch, and he wants to take all his clothes off and just rub against everything.

But John has self-control, and his monthly six to nine hours of heat on the 17th barely disturb his schedule. He rarely even needs to rest the next day, whereas most omegas are knocked off their feets for one to three days after. So John just accepts it as part of his nature: mildly annoying, but bearable.

Even pleasurable, after he and Sherlock became intimate. Sherlock can sense the changes in John starting about the 15th, and he becomes pleasantly facilitative. He'll properly package and label his experiments, go to Tesco's to stock up on food, and actually play his violin - rather than torture it. If they are already on a case, Sherlock becomes rather protective. If Lestrade tries to call them in, Sherlock refuses to start any cases between the 15th and the 18th.

Sherlock doesn't say, but John knows he is concerned that John will be in the wrong place at the wrong time when the heat starts, which has the high probability of attracting unwanted attention. John can take care of himself, but it is...nice, sometimes, to see practical demonstrations of Sherlock's regard for him. Lord knows the alpha never says what he's feeling.

Which is why when the 15th comes and goes, and Sherlock's behavior has not altered in the least, John feels just a bit disappointed. He pushes the feeling away - Sherlock's been on a smuggling case since the end of last month, and his full attention is on gathering evidence against the criminals.

The 16th comes and goes. Sherlock emerges from his room in the morning disguised as a homeless person, and he is out the door without so much as a bite to eat or a goodbye to John. John just sighs, wondering if he will be spending this heat alone. Sherlock has a habit of... displacing his solitary heat aids in fits of pique, so John spends the afternoon gathering and sanitizing them.

The 17th...

Nothing.

John is not concerned in the morning. He tends towards afternoon to evening heats. By 3pm, he's still not too worried - nothing incredibly unusual. He gets a little anxious as the afternoon progresses, and by 11 pm he is...

Uncertain. Nervous. Can he go out tomorrow? He hasn't missed a heat since he switched off the suppression meds. It makes him feel... wrong, somehow. He's only 35 - he's not past heat age yet. Omegas normally stop experiencing heat in the early 50s. Sometimes extreme stress will make an omega skip a cycle, but John hasn't been unduly stressed as of late - and his system usually isn't that sensitive even if he is under heavy stress. The only other time an omega misses a heat is when...

Oh.

Oh shit.

****

The next morning, John asks Mrs. Hudson to go to the store for the pregnancy test, just in case he's wrong and the heat is only off schedule. He really doesn't want to feel his blood to start warming in the middle of the street. The last time he had an accident like that was pre-Afghanistan, and John wound up breaking an alpha's arm before a beta constable escorted him home.

Mrs. Hudson looks at him knowingly, and gladly goes. John swears he can see a spring in her step - he wonders how long it will be before she starts bragging to Mrs. Turner. Mrs. Turner's married ones don't have a baby on the way.

John sits down heavily at the thought that he likely has a baby on the way. Half-John and half-Sherlock.

Sherlock.

John wonders how he will feel about this. Sherlock isn't exactly father material - what with the dangerous experiments, and the dangerous career, and the dangerous... danger that seems to follow him around like an old friend. He keeps odd hours and tortures his violin at 3 in the morning and still craves cocaine when he's too long between cases. John does his best to get him to sleep, to eat, and to not offend anyone unduly. Now John will have to do that for two people, if he's truly pregnant - and Sherlock got jealous when John tried to keep a plant, for god's sake.

A baby takes up a lot more attention than a plant. A baby likely takes up a lot more attention than Sherlock, even.

A baby will change everything.

But the more John thinks about it - the more he wants it. A very good thing, considering the pregnancy tests Mrs. Hudson buys him all come back positive.

All six of them.

Yes, Mrs. Hudson may be just a tad excited about this baby business.

****

Sherlock returns to Baker Street at 2:30 am on the 19th. John manages to get him to eat half a piece of toast before he practically collapses with exhaustion. John is just glad he actually makes it to his bed, this time - Sherlock gets cranky when he falls asleep on the sofa for an extended period.

John helps a half-asleep Sherlock out of his clothes, leaving him in just his pants under the duvet before lying down beside him and texting Lestrade.

Case over, I take it? J.W.

John smiles, because Sherlock insisted on setting his mobile to add his 'signature' to the end of every text automatically. John thinks that at least half the reason he did it is because it makes John think of Sherlock every time he texts.

Yes. He got home okay?

Passed right out. J.W.

Sorry about your 17th.

John smiles again. Lestrade is a beta, albeit a very confident and self-assured one. He's not affected by an omega's heat in quite the same way as an alpha, though he can still sense it. He also gets a bit flustered when anyone brings the topic up in conversation, so John has taken to referring to his heat as "his 17th".

Don't worry about it. J.W.

Really, it would have been annoying but tolerable if he had to pass the heat by himself. John would put up with more than a little discomfort to get those smugglers off the streets.

****

Sherlock is still asleep when John wakes up the next morning, so he heads to the kitchen to make some tea and breakfast. Then he settles down in the sitting room to type up their last case. Sherlock makes his way out sometime after noon - still in his dressing gown, of course. He flops down on the sofa immediately, and John brings him some food before sitting down again.

"It's the 19th, you know," John says, deciding to get this conversation out of the way quickly. He gave the pregnancy tests to Mrs. Hudson to dispose, so Sherlock wouldn't see them in the bin and deduce it himself.

Sherlock blinks, obviously shocked. He sits up immediately.

"No. No, that's not right," he argues. "I could swear it was the... the 13th? The 14th? Your scent hasn't changed yet."

"No," John replies. "It hasn't."

Sherlock frowns, getting up to move a few books around.

"You found the aids," he states, his expression disdainful.

"They do make things easier," John tells him. "But I didn't have to use them."

Sherlock's face pales dramatically.

"Did... did someone?" he trails off, before dashing up to John and examining him minutely. Then he goes back to his room, before heading up the stairs to look at John's. He flounces back down to the sitting room after a few minutes.

"You didn't have your heat," Sherlock announces, frowning. "Did you go back on your heat suppression medication? No. No, I would have seen you take them. Not to mention it tends to sour an omega's scent. You're still on the normal contraceptive. Stress can shift the cycle, but even during high-stress cases you have experienced your heat on precisely the 17th for as long as I have known you."

"That's true," John responds mildly.

Sherlock looks at him, a confused expression on his face that slowly, slowly shifts to understanding. He sits abruptly.

Right on the floor. He doesn't even make it to his chair.

"You're pregnant," Sherlock states, sounding dazed - but certain.

"Yes," John answers, sighing and sitting next to him on the floor. Best to have this conversation on an even level. "I know it's a bit of a shock, but no contraceptive is 100% effective."

Sherlock doesn't respond. They sit there in silence for a few moments before he stands - just as abruptly as his sat - and practically sprints to his room. John can hear the lock slide closed behind him.

Well, it could have gone worse.

But it definitely could have gone better.

****

John knocks on Sherlock's door a few hours later, but there is no answer. He frowns, because Sherlock really needs to eat something substantial. He goes to get the key from the cleaning supply box (the one place Sherlock almost never looks) and opens the door.

Sherlock isn't there.

John sighs, looking towards the open window. Of course Sherlock doesn't need doors to leave. John just wishes he would use them anyway. He closes and locks the window, so Sherlock will have to come back through the door like a normal person.

****

Sherlock doesn't return for another three days, and John's patience is wearing thin. It is fine if Sherlock wants to have a bit of a panic - John just wants Sherlock to panic at Baker Street so they can actually talk about this. Sherlock returns the morning of the fourth day. John is reading the paper in his bath robe, fresh out of the shower and looking for something to do. Mrs. Hudson brought him a plate of biscuits, tutting over Sherlock's absence the entire time.

"Hello," John says, keeping his voice and expression mild with sheer strength of will. He wants to get up and shake the bloody bastard. Sherlock left his mobile at Baker Street, so John hasn't even been able to contact him. The only way he even knew Sherlock was still alive was because Mycroft contacted him at the end of the first day to congratulate him on the happy news and promise to have his people watch over Sherlock.

Sherlock doesn't answer his greeting, just stumbles over to kneel at the side of John's chair. He looks at John's abdomen, his hand tentatively reaching forward before lightly ghosting against John's robe.

"I'm sorry," Sherlock mumbles, the words soft and hard to make out.

"What for?" John asks, not ready to let him off the hook quite so easily.

Sherlock looks up at him with guilty eyes, but doesn't answer.

"Why are you sorry?" John repeats. "For leaving without telling me? For forgetting your phone so I couldn't even ask if you were alright? For making me worry? Why?"

"All of those," Sherlock tells him. "I'm sorry for all of those. You're pregnant. Negative emotions can affect the development of the baby. I shouldn't have made you worried. Or angry. I'll do better."

John sighs, purposefully relaxing the tense muscles of his shoulders.

"Well, okay then," he says. "Would you like a biscuit? Mrs. Hudson made them - they're quite good."

Sherlock blinks at him, glancing over at the plate of biscuits before tentatively standing up. He still looks a bit lost, so John stands and pulls him into a hug. Sherlock grips back tightly, resting his head on top of John's. John just can't help himself:

"Man, I sure hope it's yours," he whispers, trying to keep his voice as even and seriously as he can.

Sherlock's grip immediately tightens around him, and he grabs John's shoulders to push him back and look down into his eyes.

"That's not funny!" Sherlock tells him. "I do not appreciate your attempt at humor, John. I... you wouldn't... you didn't..."

John leans up and presses a soft kiss to Sherlock's lips.

"It's yours," he says firmly. "I certainly didn't have sex with anyone else during my last heat, now did I?"

A smug smirk tugs at the corners of Sherlock's lips at that statement.

"No," he agrees. "I was exceedingly thorough, and it was my sperm that impregnated you despite contraception. I must be extremely virile, even for an alpha."

John just snorts and leans his head against Sherlock's shoulder, pulling him back into another loose embrace.

"Yeah, yeah. You big, strong, virile alpha you," he murmurs ironically. "Just don't forget who has to actually carry your ridiculous crazy genius sprog."

"I won't, John," Sherlock replies, holding him close. "I won't."