Hey.
Will try to bring one of my ideas presented briefly in on one of... foreign language chat threads earlier, but modify and expand it a bit.
Maybe imagine the world overcome come king of hard climatic or space originated disaster which leads to catastrophic global famine. And one group of, we can name it, "elites", developed one original method - they made and spread some kind of genetically modified human virus which dramatically changes female body functioning. This virus made women lay eggs, but not instead human child birthing, but in addition, regardless "normal" pregnancy. It starts to work from fertility age and, from some moment, forms eggs inside girls wombs - one big egg regardless on impregnation, sex acts and so on; it grows for month or maybe two, and then girl must lay it "naturally", after it next egg start to form almost immediately, and circle starts over. This egg size grows from circle to circle - beginning from relatively small one and gradually becoming bigger and bigger, heavier and more voluminous. It can start from something like geese egg size for beginning (for teen girls) which is not so hard to push from their bodies - of course, it brings some troubles for unprepared young girl, but nothing impossible, but then it grows bigger, and, for example, 18-19 years old girls must birth ostrich-size eggs or even bigger, which is comparable with human child or bigger. And, of course, girls struggle hard with such large eggs... laying become feels like natural birth or even harder, with painful labor and long exhausting pushing stage, crowning through burning stretched vagina, for long hours... and not once for her own wanted baby but every few weeks for goddamned egg!
This virus spread over all world, over countries and cities populated by poor survivors and refugees, and they, trying to adapt to it, created different infrastructure for helping poor girls and women... special birthing rooms in schools, colleges, offices and even just in different public places, equipped with birthing chairs or beds, ropes to grab during pushing, towels and blankets, water. Every day these rooms are occupied with poor girls, desperately pushing their unwanted eggs outside their vulvas, screaming and grunting from pain through gritted teeth... somebody - with support of other girls or even some primitive medical help, somebody suffers alone, pushing with all their might, trying to "birth" giant melon-sized egg. Or lay eggs at home, on own bed, or bath… or even just on streets or wilderness, having zero help and support relying only to own strength and will. Only way to break this dreadful circle at least for some time is to get pregnant "naturally" with human child, so girls, almost just after next laying, rush to mate with men, hoping to get pregnant and "rest" a bit from eggs torture. But... this world passed catastrophe, so this it not the best place for newborn child (especially for girl..), people who not belongs to "elites" are poor and weak, with great lack of possibilities, so having a child is always serious hard decision. Egg laying requires lot of strength, so girls are made to work their bodies hard, training their abs for harder pushing, breathing and general endurance from very young age to handle lot of big egg laying "sessions", and, of course, for maintaining their bodies in condition and shape attractive for men even after dozens of "pregnancies" and "births".
Eggs - yes, they are absolutely inactive, nothing can hatch from it, and they use only as proposed by "elites" when they created the virus - as food rations material. Girls just sell eggs in special points, exchanging it for some essential products like medicines, high-quality clothes, electronics for their families, or just cook it and eat. Price is obviously depends of egg size, so, of course, women have some king of "interest" in laying bigger and heavier eggs... even it become unbearably hard and agonizing.
About "elites" group itself - let's propose, that they live in separated secure areas which are much better suitable for life, and maybe even comparable with life style before disaster. Virus affects them, too, but we can guess that their scientists discovered some way of "protection" - maybe, they can inhibit eggs size growth so laying stay relatively easy for "elite" girls for entire life, or even invent cure and free them completely, letting them live as before catastrophe.
I can continue expanding it a bit - for example, let's imagine "elites" scientists projects related to increasing virus "effectiveness" and, as result, food supplies. They can experiment with virus strains and use it on some "testing grounds" or on groups, increasing maximal egg size growth to some limit when girl anatomically can handle it and push enormous egg through her vagina with using her muscles strength and willpower only, without surgery and any other medical invasion unavailable for poor ones... or maybe increasing growth speed which leads to laying "full size" valuable eggs earlier, not only by ones who reach age of 18-20 years. Or even the most "dark" way - decreasing minimal age of virus effect starting so eggs can be layed by much younger girls, maybe even from very beginning of puberty... make them suffer more and more for supporting "elites" prosperity!
Or other scenarios when virus development takes out of control and it started to mutate, changing it effect... for example, making eggs not bigger, but transforming it from flat-shelled to spiked which make egg laying process crazily excruciating and traumatizing for girls, or changing its shape to more spherical, which is more "optimal" for its weight and value as food ration, but begin require much, much more muscles strength and endurance during pushing due to risks of receding it back between pushes and need to start laying from the beginning again and again...