1557 illustration of a woman pregnant with 11 foetuses, supporting the weight with a large girdle. According to the accompanying story, this is her second pregnancy; her first was of nine.

From Prodigiorum ac ostentorum chronicon by Conrad Lycosthenes.

Now, it's very tempting to immediately call bullshit on this story, as pregnancies with a very high number of foetuses are often linked to fertility treatment, which didn't exist in the 15th century when Giovanni Pico della Mirandola told the story.
It becomes even more tempting to dismiss the story out of hand when you look at other things which turned up in the same book, which included things such as jaunty baby with abdominal heart, concerned torso dude, Chicken Legs McLionman, and whatever the fuck is happening here.
However, we'll bite. No question is too small for the Vagina Museum. Could a woman in the 15th century give birth to 20 babies across two pregnancies?
First of all, we'll turn back to Prodigiorum ac ostentorum chronicon. As well as reporting some entirely bizarre stuff, it also recorded more normal wonders from around the world. Such as Halley's Comet. Or moose. Or rhinos, which it admittedly embellished with a fancy costume.
@vagina_museum I love the mischievous little grin in that moose! He just did a fun little prank behind him and is giggling thinking about it. Absolutely adorable, would be friends with this moose.