how do you know if your having twins are triplets?

I thought the original question, although this thread does go back several years, was how many children is a pregnant sim going to give birth to as they are now, not how to influence the outcome -- there's several in-game ways to do that and Dr. @CravenLestat mentions a couple of them. But I'm a little more concerned that the good doctor seems to be mixing up lab samples from pregnant human sims and stray dogs again. :p