Planning for a baby to arrive is as bad as planning for the end of a deployment...
In 2008 my husband was supposed to arrive home from Iraq on a Monday. Instead we got updates all week long about when they'd actually arrive. By the time they did show up, it was late Friday night. And a few of the parents who had come into town to spend a week with their single soldier would have to leave to fly home the next day. They wasted their whole week in town waiting for their child to return from Iraq. I felt so bad for them.
And now I find myself remembering this as I'm trying to organize family coming into town, because my husband is (probably) returning from deployment right at the same time as I'll be giving birth to our baby. Unless he's late. Or the baby's late. Or the baby's early. Or he doesn't get permission to come home after all.
How early should my mom come just in case my husband's not there? I don't want to be in the delivery room alone, but I also don't want to have her come out too early if I'll follow standard wisdom and carry my first baby well past my due date. And when do I arrange for my in-laws to come? They'll want to see their son for the first time in over a year, and also their new grandbaby, but when do I tell them to buy plane tickets? This stuff is hard to arrange in advance, and everyone lives 1000+ miles away. Including my husband!
Having a baby is like the end of a deployment: you know it's going to happen sometime, but the window of possibility seems mighty big when you're trying to make plans around it.