If you're talking about how many you can be pregnant with then I believe it'll be 55 at the moment, but I need to rework the pregnancy tables down the line. At the moment your fertility dictates which pool of numbers the game picks from then it's an rng roll to see how many you're actually pregnant with. So, while you could have some astronomical fertility rating, you have just as much chance to be pregnant with 55 vs if you were at the bottom of that tier. Plus 55 isn't a good representation of the final size I don't think.