The pregnancy will be harrowing, regardless of what kind of twins you have. Count on something unusual/scary/confusing/gross coming up at some point, and try not to take it too much to heart. The human body is stretched to its limits in any pregnancy; multiple pregnancies start to seem like science fiction the longer you think about them (wait. How many are in there right now?? what!??). So find great care providers and trust them, and remember it will all be a blur from here on in.
There’s a good chance that, if you have twins, they will spend some time in the hospital after they are born. Twins, even lower-risk twins, are often born prematurely. However, hospitals are amazing these days. While your twins are in the Intensive Care Unit, it will feel like the longest weeks of your life, but chances are, they will be totally fine at the end of it. As long as the days felt while they were in the hospital, however, they will feel twice as long when they come home. In your mind, you will be begging for a nurse to come and feed your children just once more so you can get an extra hour of sleep.
If you have identical twins, get used to them drawing lots of attention when you go out in public. The attention is not so much directed at them, but in your general vicinity, like whispers on the sidelines but everywhere you go. In fact, it’s kind of fun if one parent takes both twins, and the other parent walks 20 feet behind them to observe all of the faces of people reacting “Did you see those twins? OMG. TWINS!”