At what now?

Artificial wombs? Amentans don't have them but they have science fiction containing them and they aren't too farfetched.

They have incubators for prematurely-laid eggs but artificial wombs to start gestation from the beginning aren't something that's come up in mermaid science fiction much.

Maybe it would work and then they could just not miscarry small batches.

Maybe!!!

The suggestion is immediately submitted to some extremely official-looking medical forums. 

Awesome! The Amentans really really really want to solve the merpeople's problem, it's so tragic.

It's so tragic! It's so so much better than it used to be but that's...not saying much. 

That's really not saying much! They have some science fiction about r-selected sapients but it mostly assumes that for whatever reason those sapients are, like, okay with being r-selected.

r-selected?

Having a lot of babies so that most evolutionary selection happens in infancy. They're not classically r-selected - that conventionally refers to animals which (on Amenta) don't rear their young at all, let alone adopt others' - but it being impossible to personally invest in all of the offspring you have is the key thing there. On Amenta most mammals and birds can at least try to rear every baby that they have, although the state of nature still involves high mortality rates.

Oh. They don't have that as a bright line distinction, they just have a spectrum of involvement with the lives of offspring. Mermaids are pretty high on the spectrum, although they're topped by most birds, which don't tend to have more offspring than they can rear. Other points on the line include species which guard their eggs ferociously but lose interest once the eggs have hatched. 

It's not a completely bright line on Amenta either but it'd be less of one if they had more of the middle-ground species like the merpeople planet does.

It probably wouldn't really be possible to create a real civilization with "pure" r-selection, not that that stops the science fiction writers. 

Nothing stops science fiction writers!

Meanwhile, scubamentans are also investigating history and science museums.

The history museum clarifies that the Southshallowshelf war was the one in which someone accidentally dropped a corpse on someone else! Here is a gallery of artifacts relating to popular religious figures! These syringes were used for lethal injections by the K'k'k'aouiiiia'keka Empire! Here is a gallery of artifacts and explanations in rough chronological order concerning a mermaid civilization which went extinct about half a millenium ago!

Religious figures! What are mermaid religions like?

Mermaid religions focus around historical mermaids who are considered to be paragons of virtue, and their practice involves living according to that paragon's virtues. Theologian mermaids are ones who read texts by and/or about paragons and debate how such-and-such a paragon would respond to such-and-such an issue that wasn't around in the paragon's time and so forth. 

Not all mermaid religion focuses around generally-acknowledged paragons; some people hold up departed loved ones as personal paragons, or otherwise use less-popular dead mermaids whose virtues they consider relevant to their own lives. 

Interesting! Amenta doesn't have a widespread comparable tradition but some famous people are widely admired.

Their tour guide, who is an extreme history nerd who has devoured every historical text the Amentans have made available, comments that if Avalor had been a mermaid she would probably be a popular paragon for civil servants. 

"Avalor was the Voan governor, right? I don't know, towards the end some pretty bad things happened on her watch."

"I didn't really understand that part but anyway we really don't like empires these days."

"Yeah, nobody likes the Empire of Oahk."

Nod. 

More history! These historical empires over here weren't as bad as Oahk or K'k'k'aouiiiia'keka but they were still not great! They had thus-and-such non-reproductive negative effects on their conquered states!

What happened to that one extinct mermaid state?

Unexpected and really big volcanic eruption. There were survivors but they got folded into other nations.