On the other show about polygamous people I recall them discussing birth control like it was a dirty little secret because it wasn't supported by their families and it was a choice those women had made that wasn't necessarily in line with the religious beliefs they adhered to.
In both families here the whole having and who is having a baby discussion seems to be a larger family issue that involves a degree of discussion between all the sister wives. And in either case it always seems to result in hurt feelings. Though I bet too the pregnant wife gets all sorts of attention not only from Kody but the other wives so it is a nice position to be in in the family. I mean really for the most part Meri had been put to pasture long ago when she couldn't have more kids.
If I were Kody and only interested in procreating with the new wife to keep the peace better (so it didn't look like I was only interested in the hot wife) I would be discussing as a family healthy and uncomplicated pregnancies and which of the wives is mostly at their age to have an uncomplicated pregnancy because as the leader of the household it would be irresponsible for me to put any wife in that position because I want to grow the family. But Kody isn't a thinking man like that. He lets the women bumble around instead of taking a leadership role.