I made a few edits to the dialogue of the story as well as fixed some errors. The basic story remains the same. If you're reading this again, feel free to let me know if it's an improvement or not.
"Doctor! Come quickly, you are needed urgently!" it was a rare occasion when Celestia raised her voice, and when she did it caused every pony within earshot to take pause. Even the attending physician stood dumbfounded at the closed door until he heard Celestia speak again, "Please, doctor..." her voice quieter now, weaker, tinged with desperation.
That snapped Dr. Sawbones out of his attentive stupor, "Ahh, yes. Of course! Nurse, you're with me! Orderly, get the visitors out of here! The doctor flung open the door to the patient isolation room.
Princess Celestia stood at the entrance, her normally billowing mane and tail hung flacidly, the radiant energy of her aura was dim shadow of what it once was. Dr. Sawbones was taken aback and panicked at the pathetic state princess Celestia was in. "Princess! What in the name of the sun and moon happened? Nurse! Get a gurney in here! Fetch the CMO! This is an emergency! Lock down the hospital! We can't have word of this getting out!".
Orderlies started rushing about, following the Doctor's orders. Princess Celestia shook her head, "I am fine, Doctor. I just need some rest, perhaps a bit of sweet tea. He is your patient." She steps back looking at a maneless, blank flanked unipeg foal lying on the bed, wheezing softly, struggling to breathe.
Dr. Sawbones stared at the young foal for a long moment, he didn't look like a newborn, but rather a foal of 7 or 8 years. Certainly not the creature that was brought in. "B-but Princess. Who is this? Where did he come from?". The doctor demands to know. "Where is...".
"He is my son." she interrupts, "Please, he won't survive without help." The weakened princess gives the doctor a pleading look.
Dr. Sawbones heart skips a beat, and in the space of that missing heartbeat, he steels his reserve, "Someone take care of the Princess. Nurse! Prepare the positive pressure breathing apparatus! We have to maintain his airway! Get some diagnostic equipment in here! And someone summon the pediatrician!".
Princess Celestia is led from the now extremely busy ward by a pair of Royal guards, "Please take me to my room." Celestia requests of the guards. The princess is led into her sleeping quarters. When they arrive, she sees Luna pacing back and forth, disturbed by the warmth of her sister's energy suddenly peaking, and fading away,
Luna rushes towards her sister, an expression of worried panic on her face. "Tia! Tia, what happened? I felt your aura flare and then I couldn't feel you at all until just now." she explains, forgoing the royal dialect for the familiar tone of voice she always takes with her sister. Celestia is levitated by Luna to her bed then covered by her silken sheet.
Celestia looks up at her sister, an exhausted smile on her face, "You'll need to set the sun, tonight auntie Luna." are Celestia's final words before closing her eyes, a blissful smile on her face as she sleeps.
Luna left her and Celestia's room to leave her in peace to sleep, satisfied that all that Celestia did was to severely over exert herself. Luna heads to the hospital where her sister was to get a full report as to what exactly happened. The guards part the crowd of curious ponies gathered at the hospital to allow Luna to enter. She is escorted to the patient isolation ward, then is briefed by a nurse before entering the room.
Another piteous sight greets Luna when she walks in, a pinkish/white unipeg colt lying a sleep on his side on the hospital bed. A plastic mask covering his muzzle with a hose that leads to a contraption that helps him to breathe. She can tell this pony is brand new to this world, his fur had only just begun to grow in, the pink was from the color of his skin. Luna figured by the time his coat grew in he'd be all white, save for a darker patch around his right eye. The colt had no mane nor a cutie mark as of yet, and his horn was just a tiny nub sticking out of his forehead. She also couldn't help but notice that this child was clearly not the correct size and shape of a newborn, but at the same time not developed enough to be the school-aged child he was tall enough to be. Despite all her questions, she could sense only one thing for certain: This was indeed Celestia's foal.
Luna walks out of the isolation room, meeting Dr. Sawbones in the hallway. As soon as the doctor bows, Luna begins her interrogation using the customary Canterlot royal dialect, "At ease doctor. We must know. Will yon child survive?".
Dr. Sawbones immediately stands, "I believe so, princess. He's been improving steadily since he... umm... Appeared.".
Luna begins pacing back and forth in front of the doctor, interrogating him, "We wouldst known if mine sister was taken with pregnancy, or if she was taken with a special somepony and we KNOW she is not given to..." She stops herself before even mentioning the possibility of a secret one-night lover, "In which manner mine beloved sister did birth this child? Whom sired this foal?" she asks sternly.
The doctor stammers, feeling suddenly like an enemy spy or having to report why something went horribly wrong, "I... I don't know, P-princess. It-it-it's really quite obvious when a pony gives birth, especially a child that size and-and as far as we know Princess Celestia has never been pregnant, at least as far back as we keep records. We can do a blood test, and find out... Maybe.".
Luna signs, she'd know... Anypony would know just by the smell of the room if a pony gave birth there. She would have smelled it on Celestia as well. It was all too confusing for her. Celestia wasn't pregnant, she didn't give birth in as much one normally would, but she could not deny the odd little colt lying on that bed was Celestia's child. "Make it so." Luna declared officially. "Henceforth, upon the time this art sorted we implore not a word breathed to anypony. Thyself and thine staff art tasked with the well-being of yon foal. We bestow authorization to any and all resources. Take care that no attention is brought upon this hospital.". Luna orders.
Luna kept watch over the kingdom for the next 2 days, taking the responsibility of raising and setting the sun and moon while her sister slept. She was exhausted from the schedule she had to keep, Luna caught herself napping in the royal hall during quiet moments. She gained a new respect for her sister for having this responsibility for a thousand years. Luna cleared the calendar, for the week, just in case. Luna delegated tasks to the various ministers, giving them carte blanche with royal business.
High noon on the second day, Luna woke up from one of her unscheduled naps disturbed by the noise of munching, lip smacking, clinking of plates, and even a polite belch. Luna opened her eyes to find her Sister Celestia before a smorgasboard feast of pastas, pastries, cakes, salad, pickles, wines, and ice cream. Luna watches dumbstruck as Celestia uncharacteristically gorges herself on the odd assortment of foods. Luna sits up, staring at her sister incredulously, "Tia! Have you taken leave of your sanity? What are you DOING?!".
Celestia pauses her feast, a spoon with ice cream garnished with a pickled radish hovering near her muzzle, "Having lunch." she replies obviously. "Don't mothers usually have increased appetites for odd foods?" she asks, smiling blissfully, her mane once again billowing in an unseen breeze. "Did you have a nice nap?" she asks before nomming down her pickle ice cream sundae.
Luna is mostly relieved to sense her sister's aura back to it's usual brilliance, perhaps a bit more radiant than usual. She attributed that to the rest her sister had, "Yes, mares usually have an increased appetite when they are PREGNANT." Luna retorts, then begins her interrogation. "How did you have a foal? Who's the father? How did you keep your pregnancy a secret?".
Celestia finishes her ice cream, then downs a goblet of rose nectar, sighing satisfied after the extended chug "Mmm. Is it me? Or is the ice cream especially delicious today?" she asks, avoiding all of Luna's questions.
"Tia!" Luna objects, stomping her forehooves petulantly, the effect muted by the pillow she sits on.
Celestia giggles mirthfully, nuzzling against her sister, "Forgive me, Luna. I just got up a few hours ago. You must be exhausted from taking on my responsibilities. Here, have some pie, it's delectable. We're going to pay your little nephew a visit after lunch." A slice of strawberry rhubarb pie hovers tantalizingly in front of Luna's muzzle, supported by Celestia's levitation spell, "If stilph haff to nambe hib." the princess muffles around a mouthful of peanut butter, ginger and mustard sandwich on pumpernickel bread.
Luna takes a bite of pie, watching her sister eat. She knows there will be no answers when her sister has gone silly. Though she knows Celestia uses her silly act to cover up stronger emotions. She just has to wait until Celestia's true feelings break through that silly veneer. However, the Sun Princess' odd food cravings are a new thing. Luna hadn't ever seen such behavior from her sister before.
Lunch went on for 30 minutes, and in the end, Celestia's eyes were bigger than her stomach. She invited the guards and servant ponies into the royal sitting room to finish the considerable amount of food she had left untouched.
Both princesses took a carriage for the short journey to the hospital, accompanied by a phalanx of guards, the guards would have followed them both in to the hospital had princess Celestia not ordered them to stay outside. She then promised them all that they'd see the new prince in good time. All of the guards stared at each other wide-eyed in shock, having not heard of the princely foal thanks to Luna's order of secrecy. The rumor mill officially opens for business.
The new foal made remarkable progress in the two days Celestia slept. After the first night he was taken off the respirator, the afternoon after he was sitting up on his own. By the morning of the second day his snowy white, save for a round patch of black fur over his right eye had grown in, masking the pink of his skin. Even his mane and tail had started to grow midnight black hair, just barely longer than his body fur. When the royal sisters entered the ward they found the foal laying on his belly, his legs folded under him, his wings folded at his sides. He faced his nurse, his mouth open, and his tongue out.
"Say 'ahh'." the nurse requests, levitating a wooden tongue depressor against the foal's tongue.
"Ahhhhhhhhhhh." the colt replies.
Celestia beams with felicitous joy, hearing her son's voice for the first time. She rushes to the bed, wrapping her forehooves around the colt, nuzzling his cheek and neck, "Ohhh, my baby's first word!". The foal squeaks in surprise, his wings flaring out from the startle, even the nurse is startled.
"P-Princess? I wasn't told you were coming! We would have prepared!" The nurse stammers.
After a moment the foal looks at the pony that's nuzzling him furiously, it takes him only a moment to realise... "Mama?" he asks to the abject shock of Luna. The nurse is a bit less surprised as the foal uttered his first word the night before, but if the princess says 'Ahh' or 'Mama' was his first word, that's the story the nurse was going to tell.
Celestia nuzzled her colt, tears of joy in her eyes, "Yes, yes, I am your mama. I am your mama." she holds her colt for a good long while, the little colt licks the tears away as they roll down her cheek.
Luna, smiles faintly. She does have questions, but the joy in her sisters heart convinces her that while the circumstances surrounding the colt, as well as the colt himself are odd, neither one of them is particularly harmful.
Dr. Sawbones, enters in behind Luna, she stops him, and silently gestures for him to go outside of the room. Once out to the hall, Luna asks the doctor, in her royal dialect, for the results of the blood test. The doctor makes his report, nervously, "According to the tests, princess Celestia is absolutely the colt's mother. As for the father..." He pauses, sighing, "We can't find a match. We checked every living stallion we have records for. We even started checking the blood against mares. There is no match that we know of. I have no explanation."
Luna nods, "We see. And what of the foal's recovery? seemingly he dost understand speech, as well dost speak. Pray tell how a newborn knowst to speak within two days?" she asks.
The doctor wipes some sweat from his brow, "I don't know. It's a bit of a miracle, actually. He woke up yesterday afternoon, crying. His milk teeth had erupted all at once, the poor boy. We numbed him up, and by the time the benzocaine wore off his milk teeth had fully developed. We realised he could talk last night when he told us he was hungry. His horn grew to a hoof width in length in the same amount of time. I'd say he's developed to a foal of the age of 8 in 2 days. He's still a bit tall and gangly, but I feel he might gain weight once he starts eating regularly." he explains.
Luna looks back to the door, hearing her sister fawn over her new foal. She looks back to the doctor, "How long must the foal remain in thine care?" she asks.
Dr. Sawbones shakes his head, "He doesn't. He's stabilized, other than being an extremely odd case I see no medical reason why he can't go home.".
Celestia opens the door with her magic, "Did you hear that? We can go home." she asks the foal, who nods in response. Celestia levitates her foal from the bed, his skinny, gangly legs dangling beneath him. She slowly lowers him onto his legs. Once his full weight is on his legs, the little colt's knees immediately buckle, sending him down on his belly. Everypony, save the princess gasps, making a move to help him up.
Celestia shakes her head, causing everypony to stop "No. He can do it, can't you dear?" she says with a smile.
The colt plants his hooves on the floor, slowly lifting up his body on shaky beanstalk legs. He takes a step forward, his knees buckling again, but he catches himself from falling. The adults look on expectantly as the colt takes a few unsteady steps before starting to walk slowly, but steadily. Celestia beams with pride as her foal takes his first steps.
Luna smiles, looking from the foal to her sister, speaking familiarly "Well? What's his name, Tia?" she asks. As the little foal continues practicing walking down the hall.
Princess Celestia takes a deep breath, sighing contentedly, "My son's name is Soul Strider." she declares.
In the next second they all hear,a soft 'tump-thump-tump-tumpitta-thump-bump... -gaaasssp-...WAAAaaahhhhhh!' from the stairwell.