Some ideas about pregnancy from insects and other.
Expand the parasitism system by allowing the parasites to fertilize the heroine's eggs.
Main idea:
If the heroine does not remove the parasites from her uterus, they fertilize her again and again (even while she is pregnant with them)
Since the parasites are small, there are no visible changes until the heroine becomes pregnant with a large number of parasites.
The heroine can give birth when she is pregnant with a large number of parasites, but this will not result in the removal of the original parasites and after a while she will be pregnant again.
Additional kinks:
Parasitism incest (or more impregnation)
Offspring from parasites, just like "fathers", strive to fertilize the heroine's eggs.
Which increases the growth of the heroine's belly.
For example, the heroine is pregnant with 100 parasites, this is not visible on the belly.
The heroine is pregnant with a thousand parasites, this is already an average level
And 2500 is already the heroine's belly as the 9th month of pregnancy.
The numbers are invented as an example, because I do not know the sizes of parasites.
Womb parasitism
parasites can live an unlimited amount of time in the uterus due to the fact that they form a kind of placenta and receive nutrients from the uterus without harming the heroine.
Ovary parasitism
If the heroine naively allows the parasites to remain in her uterus for a long time, then the parasites merge with the ovaries (indirectly, without guro, gore, blood, ryona, bad end, any harm, etc.).
Then there are two versions:
- These parasites become difficult to extract
- Either these parasites cannot be extracted (an option for those who want to be in the place of this heroine and get pregnant at most from slimy nasty worms)
In addition, they enhance the fertilization of the heroine's eggs and make her ovulate constantly.
Thanks to the fusion with the ovaries, the parasite receives nutrition.
Any small insects are parasites
All small insects can parasitize and fertilize the heroine from slugs to cockroaches and earthworms.
Naive heroine - accidental "crawling" of insects into the uterus
The heroine walks through the forest and ignores the events "it seems something is crawling in panties", after which a small insect crawls into the uterus and becomes a parasite.
(so as not to create them as enemies, or you can create them as opponents "a swarm of small slugs")
Example:
Cockroach:

Earthworms?

Sea creature:

Worms:

