Add-ons- rapid pregnancy, orgasmic birth
Despite how straightforward this "experiment" seemed, it didn't do much to curb your nerves.
While you and the rest of the world were still reeling over the confirmation that humans most certainly were not alone in the universe, the government higher ups (who had apparently been privy to this fact for years) were already well into various negotiations and experiments with the extraterrestrials, such as the one you currently found yourself volunteered for.
You see, the other life that was out there was dwindling, much faster than they would like. So once it was revealed that our genetic makeup had even the possibility of compatibility, talks of crossbreeding soon followed.
Everyone stood to benefit, it seemed; they'd postpone their extinction, and humanity would have the chance to access even greater evolution. As for you, well...you'd just have to find out.
This brought you to now, sitting in a small observation room. To your relief it wasn't the metallic, brightly lit room you were dreading, but rather was lit by a dim, warm light. The aliens, which were surprisingly similar to the greys of pop culture, had made it clear that harsh lighting would disturb and potentially damage their offspring's eyes.
Your eyes flicked to the two way mirror on the wall facing you, where scientists of both species had already been monitoring you for a couple hours now, starting right when you'd been successfully inseminated. Mentally you ran through how the experiment would go, provided it went smoothly; you were to remain in the observation room for the entirety of your pregnancy, which if the aliens were to be believed would be blissfully short, three days to a week at most. You were also to give birth by yourself, they would only intervene if it seemed like things were going south. The reason for this was apparently so the experiment wouldn't be sullied by invasive methods from either side; simply put, the baby would dictate how it would be born. The last thing, something the translator had relayed with an interesting expression, was that this experience would be "far more pleasant than you would expect".
Ten hours in, the scientists in the next room watched as you repositioned yourself on the bed provided. The thin fabric of your hospital gown, which had been baggy on you that morning, was now stretched tightly over your newly swollen belly. Every now and then someone would come in to measure and photograph you, which you still found yourself being self conscious of every time.
To the untrained eye it looked like you were experiencing a normal pregnancy, except for a couple odd details. Your belly was flushed with a faint purple hue, which they had hypothesized was the fetus' blood mixing with yours in the placenta. The other detail was that you were sweating, but not with exertion or discomfort, far from it. That cryptic little hint from the translator turned out to be alluding to a natural chemical released by their hormones, which apparently induced an aphrodisiac effect in humans.
The scientists encouraged you to respond to any impulses or urges you felt, provided that it wouldn't harm you or the baby. While you were still very aware of being watched, the sensations became gradually impossible to ignore.
Three more hours went by and you'd shed the gown, sitting upright in the bed with your back supported by pillows. With one hand you cradled your belly, now visually comparable to a full term pregnancy, while your other was nestled between your spread legs, slick sounds hanging in the air as you sunk two fingers into yourself. Your thumb pressed and circled your swollen clit as you worked to bring yourself to yet another orgasm, having lost count of which one this was.
This one felt like it was going to be different, although you were too lost in the pleasure to voice this to them. Instead your fingers worked faster, your hips lifting as much as they could, and with a cry you finally felt the pressure come to a head as you came hard. An unfamiliar sensation washed over you, and your cheeks flushed as you felt a torrent of fluid gush out of you.
Panting softly you reached down to inspect it, finding your fingers coated with a slightly viscous violet liquid, what you assumed was your 'water'. It had definitely caught your off guard, considering you hadn't been experiencing conventional contractions. Gradually you realized that it was the intensifying pleasure that was leading up to your advancing labor, not pain.
Your heart raced as both you and the scientists realized that this was progressing much faster than they'd estimated; if things continued at this rate then you'd have experienced a full pregnancy and birth in under 24 hours. Before you could think about it any more you felt the odd pressure of your belly shifting, dropping as your alien baby began its descent.
Leaning back against your pillows you spread your legs wider, giving a clear view of the flushed lips of your cunt as you moaned through another pleasureful contraction. All shyness was fully out the window now, and you could think of nothing but just how wonderful it felt to give birth, the hormones doing their job perfectly. It wasn't long before you felt the urge to push, and you gave in without hesitation, the resulting orgasm making you squirt even more of the syrupy amniotic fluid.
In the adjacent room both groups of scientists were dutifully noting everything, some of them doing their best to ignore how much the sight and sound of your birthing was arousing them. This became more difficult as they watched you beginning to crown, the swollen lips of your cunt gradually stretching to accommodate a much larger head than it would with a human baby. Surely the aphrodisiac hormones was the aliens evolving an incentive for reproducing; one is more likely to want to give birth if it feels good, after all.
Back in the observation room you were panting heavily, voice hoarse from cumming so many times over the course of the day. You obeyed your body's urges and bore down hard, fluid leaking steadily out of you as you successfully pushed out the head. The overstimulation had you mewling desperately, and as good as this felt you were ready for it to come to an end. The hardest part was done, though, and a few more good pushes had the rest of the experiment slipping free from you.
A pair of scientists in protective gear swiftly entered, retrieving the baby before you could even ask about it. A twinge of sadness tugged at your heart, but you soon let it go. After all, now that the experiment was more or less successful, you suspected you'd have the chance to do this many more times.