Overreacting?

Okay, I'm almost 18 weeks pregnant, due July 20th. I was hanging out with my sister and her boyfriend yesterday ( I try to get along with him as much as I can ). And they were talking about going to California for vacation in the summer ( we all live in Tennessee). And I was just asking when and they said July 10th-16th... so I said like being funny " well I hope I don't go into labor while you're there, you'll miss your first niece or nephew being born " we don't know what the gender is yet. And her boyfriend said " well I don't know what you expect her to do, it isn't her kid and she can't just put her life on hold because you pop a baby out before your due date when you can just hold it in until we get back ". I got upset because he basically yelled it at me so I went home, she calls me later on and said I had made him really mad for leaving and I needed to apologize? Was I wrong for being upset that my sister may not be there and for leaving when he yelled at me