Suddenly, Renee saw the translucent wall give way right in front of her - a hole opened, big enough for a few sperm at a time to swim through. As she was the only one who happened to be moving in the right direction at the right moment, she was the first sperm to arrive in the vagina. The liquid she was swimming in was different now, acidic and kind of unpleasant - she wouldn't be able to survive long here if she wouldn't find an egg to fuse with. But was there even an egg? Was this woman in the correct phase of her menstrual cycle, right after ovulation? Or had the egg already faded away, expelled from the womb along with the remnants of it's inner lining? It didn't matter, Renee had only this one chance.
After a long journey through the womb and up into a fallopian tube, she actually encountered a huge cell many times her size - an egg. She realized it wasn't fertilized yet as she touched it and became stuck, her head making it's way inside the egg through a chemical reaction. Then she dissolved and ceased to exist as a sperm, her DNA recombining with that of the egg to make Renee the zygote, which began to divide and grow into an embryo and embedded itself in the womb.
Three weeks later, the owner of said womb noticed her period was overdue. First she dismissed it, it had been a bit irregular occasionally. When she still felt no sign of it days later, she became nervous. Then she bought a pregnancy test.
"But we used condoms, didn't we?!" was her first thought when she saw the second line appear, the one that said she was pregnant. She was...