How do I´ve set castes to stop certain sims from getting pregnant?
Some of my towns lack of genetic diversion meanwhile, because it´s always the same 2 or 3 families getting babies (and surprisingly they don´t even have the family-oriented trait) whereas some others (some of them have the trait) won´t have any children at all. And it doesn´t matter if they live in a house without cribs and enough beds, they just give birth if I don´t end their pregnancy.
And how can I set castes to show pregnant sims when looking for demographics in MC?
TIA

Start using the pollinate command

Also story progression on specific sims can deny participation/pregnacy and stop those sims.

I have to admit the SP options can be a bit confusing until you get used to them. Under Sim, Household, Caste, Town Options,

Pregnancy: Allow Can Be Pregnant doesn't necessarily stop pregnancies from forming in other ways outside of SP, but on False prevents sims from being pregnant. That means once SP "notices" a pregnant sim with this setting on false, it will quietly terminate the pregnancy.

Pregnancy:Allow Participation is stronger and on False should be acting to make that sim sterile as a potential mother or father (or in the case of same gender I should say baby carrier or sire) even if Woohooer is in play.

Pregnancy:Allow Can Be Pregnant Caste and Allow Participation Caste do the same things, except they allow or disallow whom the other parent can be in each case.

If you don't want that but want to selectively reduce the desire for these sims to have babies subject to adjustment for trait scoring, that would be Pregnancy:Base Number of Children (default is 3). That's not a forceful way to inhibit pregnancies at all though, especially if your world is under the designated population cap as set under General Options > Options:Sims.

Pregnancy:Max Number of Children (default 0, which means no cap) is a little stronger, but only covers planned pregnancies and there can still be oopsies happening.

The number of cribs/beds has no bearing on pregnancies under SP, only the household size cap does. The beds/cribs can subsequently cause home inspection failures and can cause households to look for more suitable accommodations if they have the funds and any or available (they will stay put if not), and can prevent them from moving into a new to them home that doesn't have enough of these, but it's not part of the biological process of conception. I think Awesome handles this differently, so some players who have used that in the past think that SP takes furniture into account in the same way but it does not.

Pregnant is a MC filter option under Type of Sim. I kept getting extraneous results using that one (pets, foreign sims) long ago so at the time I set up a custom MC filter called "Preggers" or something like that to account for sims who are human (not animal), local residents, and pregnant.

Thanks for the info igazor, but: I´ve disabled pregnancy through SP like you suggested, my SP isn´t linked to whoohooer, but one of my active couple just managed to get pregnant without my will and another inactive couple has managed this as well, although I´ve disabled either Allow Participation and Allow can be pregnant! (And I´ve set a sim limit to the town which is now overstepped by 3 babies) I think my sims must love babies so much that they completely ignore me!
But according to search for pregnant sims: If I search in demographics, I can see that someone is pregnant, but not who! So how can I find out who is pregnant in a more easy way than now? ( I go into town view and look at the map tags of the residents)

On City Hall or an in-game computer, NRaas > MC > Sim > Basic > Family Tree (or something harmless like that) > Filter to Type of Sim (And):Pregnant. If you get results that don't make sense, then filter further to Type of Sim (And): Pregnant and Resident.

I will add that I've seen sims disallowed on Pregnancy:Allow Participation can Try for Baby or do Risky, but they have never succeeded. Would be curious to know if the pregnancy continues or if SP does indeed terminate it within the next sim day.

If you have the link disabled this is to be expected. If you want woohoo pregnancy to be controlled instantly by the caste system it needs to be enabled.. otherwise it will terminate the pregnancies later.

igazor+Chain_Reaction: Thank you both!
With the explanations and guides I´ve finally managed it to find the pregnant sims the easy way!
And SP ends the pregnancies within the next day, even the ones of my actives!
Happy simmer here!