You do not need any baby/toddler equipment in a house occupied by a family, you don't even need enough beds if you move the family in through edit town. However, if you use the move function on the telephone to move part of your current family out, the game does check to make sure that the home has the basics and enough beds. But, it does not check for pregnancy, so if you move a pregnant couple to a new home this way then all it needs is the basics and two bed spaces. They will raise their children quite happily as long as you do not try to play the house.
Sims are unlikely to become pregnant through story progression. And, I agree with you that this is a shame. However, story progression does fill up some empty (furnished) homes. I think it does check suitability when it does this. I am not certain though. It might be worth placing or building a couple of baby ready homes to test this.
If you are playing a fun game rather than a challenge of dynasty game, there are lots of ways of getting more youngsters into the game it story progression fails to keep the population dynamic. For example, placing a bin family into a home or creating a few pregnant couples and saving to the bin for future use.)