In preparation, I took a wonderful "Multiples" class offered by Lucile Packard Hospital; reached out to a mentor with twins; and of course followed my doctor's orders. Here are some additional tips about twin pregnancy that I'd like to pass along (all borrowed from others before me):
1) Gain as much weight as possible in the first trimester. I put on at least a pound a week. By the time I told my team at work that I was pregnant, I couldn't believe they hadn't noticed! Along with indulging in ice cream, I ate big breakfasts (and lunches and dinners!) and had snacks mid-morning, mid-afternoon, and sometimes before the evening commute. I also sometimes woke up in the middle of the night famished (which has never happened before or since). I would eat an apple in bed, loudly, which my husband said was like being in a dark barn with a hungry horse.
2) Eat protein - lots of it. I thought my mentor was crazy when she told me to get creative and eat the equivalent of six steaks per day. I'm not sure I did that, but I ate eggs and yogurt and peanut butter toast almost every morning, and I tripled my meat consumption.
3) Drink water - at least 64 oz in addition to all liquids at mealtimes. When I failed to drink two tall water bottles per day, I often had Braxton Hicks contractions. Staying hydrated keeps your uterus from contracting, so do it.
4) Speaking of contractions, stay away from them. At the end of my pregnancy, I avoided too much activity - even driving to and from meetings around Google's campus. Anything that might cause Braxton Hicks contractions, I stayed away from (including people who stressed me out!)
5) Swimming - I really had no interest doing this activity in the winter, but at my mentor's urging, and with the encouragement of a good friend who was dragging herself to the pool in the morning before work, I went. And it was wonderful! I swam twice a week throughout my pregnancy and on the day before the twins were born. (At which point the lifeguards appeared to be watching me like a hawk, lest I have an unplanned water birth.) I've continued to swim post-partum, and it's been so easy on my body after everything it's been through (although finding a bathing suit that fit me post-pregnancy was less easy).
6) Prenatal yoga - Read more about it here.
7) Know when to stop working - at some point, you may wake up and realize your full-time job has become keeping your babies inside and healthy. Honor that, and make arrangements to put your growing twins first.
Thanks to my wonderful and understanding co-workers and my supportive and caring friends, my twins pregnancy was one of the happiest times of my life. I hope it will be for you too!