Pony genetics are a fascinating and complicated area of study. Most ponies don't realize just how diverse and frankly chaotic the entire process of conception, maturation, and birth of a new foal is from a purely scientific standpoint. I've only studied the basics of pony genetics in the past, because it's never seemed particularly relevant to my own studies...for me, it's always been just a bit of idle reading on the side.
Now, though, it may very well be the most important subject I've ever studied, and I'm studying everything I can get my hooves on about it.
There's an extremely high probability that the foal now growing inside my body will be female. I mean, that's obvious. That's kind of the whole reason the Family Planning Center exists in the first place, and why I went there to get pregnant. Of course, I could also have a colt, but...I'm sort of hoping for a filly. I'm not really sure why, I just feel like I'd relate better to a filly.
But I'm not nearly as worried about that as I am about what my foal will be.
Here are some interesting statistics about pony genetics:
When two earth ponies have a foal, there's a 90% chance the foal will be an earth pony, and an even 5% chance each of a unicorn or a pegasus foal. The Cakes sort of won the lottery with their twins. The statistical improbability of two non-earth pony foals, and each being a different race...it's simply astronomical!
With the other pony races, things are a little more complicated. Two pegasi have an 85% chance of foaling a pegasus, a 10% chance of foaling a unicorn, and a 5% chance of foaling an earth pony. It's the same when two unicorns reproduce, except the 85% chance is for a unicorn and the 15% is for a pegasus.
Then you get into interracial reproduction, and the probabilities get all screwy.
An earth pony reproducing with either a pegasus or a unicorn has a 60% chance of foaling whichever race they mated with, a 30% chance of foaling an earth pony, and a 10% chance of foaling the third pony race.
And then you have my situation. I'm a unicorn, and I mated with a pegasus. There's a 45% chance my foal will be a unicorn, a 45% chance it'll be a pegasus, a 9.5% chance it'll be an earth pony...
...and a 0.5% chance I'll be the first pony in recorded history to give birth to an alicorn. It's possible, but it's never actually happened. I don't even know if Princess Celestia or her sister were born alicorns, or became alicorns later like Cadance did. I've heard that she was born a pegasus...
Oh, it would be so exciting to be the first ever pony to give birth to an alicorn!
But I'm not getting my hopes up. It's just ridiculous to assume...
Oh! I completely forgot! I haven't done any research into what happens when an alicorn mates with a non-alicorn! Or when an alicorn mates at all, for that matter. Princess Luna took me aside and confided in me that Princess Celestia has had a child before now, but it's sort of a state secret. A bit like her current pregnancy is...the princess has decided to keep her impending motherhood quiet for as long as possible. Which...won't be that long, really, now that I think about it.
Anyway, there's just no telling what her foal will be. But that's exciting too! Even though I'd really love to be able to construct a mathematical model about...
Focus, Twilight. Stay focused. Right now, I need to concentrate on my foal, and what I need to be prepared for.
If I have an earth pony foal, well...I guess there's not really much to worry about there. She'll certainly have plenty of playmates, and lots of room to run around and be all...earthy...?
Um...well...at least I live in the best place for an earth pony to grow up?
A pegasus foal could be fun, but I've heard from Pinkie Pie that Pound Cake can be a real handful. I didn't even know pegasi could fly when they're that young! I'd have to pegasus-proof the library, and...hmm. I'll have to ask Rainbow Dash about what it's like for pegasi growing up. Maybe she'll have some useful tips about pegasus foals.
I really want a unicorn, of course. A daughter who's just like me, who I can teach everything I know about magic...oh, what if her special talent is magic, just like mine? Being able to teach her all the spells I've learned, enroll her in the School For Gifted Unicorns...fun! Of course, unicorn foals can be an even bigger handful. Baby magic is wild, unpredictable, and usually gives parents headaches and nightmares. I'll never forget Mom telling me about the time when Shining Armor was a foal, and he spent an entire week teleporting everything in his diaper to really awkward places... like Dad's saddlebags...or Dad's breakfast...or right onto Dad's head...
...oh, I need to make a note to ask Pinkie Pie to place a big order of umbrella hats for me. Just in case.
Actually that'd be a real problem with a pegasus foal too. Especially if they figure out how to get the diaper off. It'd be like having a really big pigeon flying around in your house, and your nice freshly-washed mane is a great big target for...
Oh, ponyfeathers...I don't think I could deal with having a flying poo machine on the loose!
Okay, so basically I need to poo-proof and pee-proof and unicorn-proof and pegasus-proof every single thing in the library, myself and Spike included, so I'll need about...five or six hundred rolls of bubble wrap...about twenty gross of umbrella hats...
Oh boy.
* * * * *
Spike found Twilight huddled in a quivering ball in the corner of the main reading room, eyes twitching and mane splayed out in every direction. Scratching his head, he picked up the piece of parchment which had drifted to the floor near where she sat. As he scanned the shakily-scrawled checklist, he raised an eyebrow. In a flat, weary voice that spoke of long experience with his best friend's neuroses, he said, "You know, it'd be a lot cheaper just to buy leakproof diapers and safety pins. 'Cuz, you know, that's what you buy when you have a foal." With that, he padded off to scrounge for a snack.
A day without Twilight having a neurotic fit of some kind was like a day without sapphires.