Cravings, morning sickness, clothes getting too tight, feet swelling, no personal space whatsoever, etc. Don't get me wrong, pregnancy and the time afterward is amazing, and it's the most fun I've ever had in my life (except for the morning sickness), but be prepared.
No one knows any boundaries, and everyone wants to ask you a million and one questions, as well as rub the belly for good luck or whatever the old wive's tale is.
You can expect to be tired almost all of the time, as well as being constantly hungry but not wanting to eat because you'll get sick afterwards.
Your emotions are going to be ALL over the place, and your sense of smell is like a dog's. I remember the day we found out, Blake got a Big Mac from McDonald's and the smell of it made me sick almost immediately.
Be prepared to answer the same questions over and over again, because it'll never end.
But most importantly, be prepared for it to be like you don't exist after that little one is born, because every bit of the attention and affection will go straight to the baby.