Although this isn't a question directly related to sleeping only, I still think it's a good one for discussing the more "stable" age of 2 years old. I wanted to post this question ASAP since it comes from a mom, K., due with her second child in SIX DAYS! My guess is there won't be a lot of blog reading in the near future for her…

I love this question because there's just so many factors to consider and so many of them touch issues that many of us have had to deal with. I'll tell you right now I won't nail them all. But let's try to take this apart so we can see what this decision will really entail. K's done a great job of thinking all the various parts of the transition through. The main concerns seem to be:

1. Is this an ok age to make a bunch of changes in a child's life?
2. How much change can a child take without some significant level of distress (which, of course, K doesn't want to inflict on her daughter)?
3. What sorts of things are there to consider in order to make this transition go as smoothly as possible?
4. How will K's daughter respond (behaviourally and in terms of sleep disruptions)?

There's one more issue that I think is at stake here, although K doesn't mention it explicitly and that is:
5. To what extent is it ok to prioritize my own professional and personal preferences over some level of distress from my daughter?

All of these concerns are so intricately intertwined that it's tough to deal with one without considering the others. The bottom line is this decision will be about balancing the various needs of all family members. Let's start with #1: This is a relatively good age to go through changes in the child's life. Your daughter is just heading out of the toughest part of the 18-22 developmental upheaval. Of course, these are rough estimates of age boundaries so it would have been nice if your daughter was slightly  older, but still, she should have covered most of the crazy neediness/clinginess/crabbiness by then. But by 22 months or so, your child is more calm, more stable, and more secure than she was just recently. The massive cognitive changes ushered in by the 18-22 month shift have begun to consolidate. She has gotten used to being a social player in a social world. She understands what you require of her at meal-time and bedtime. Which means that she understands rules and she can adapt to them if she has to. This age can be a real delight because they start getting how fun it is to FOLLOW rules and to be a part of the family in whole new ways. But they're also now attuned to separations in a way they weren't before 18 months or so. You’re dealing with a child who is a lot smarter and more verbal than ever before. Driven by insecurity and anxiety about separations of any sort, these skills will be put to use to get your attention and comfort as much as possible. But still… making the big changes you're considering will be a lot easier now than at 2.5  years old.

#2 is about how much change is too much change. There's no REAL, data-driven answer to this of course. It all depends on the child and her sensitivities, it also depends on the TYPE of change and it also has a lot to do with how the parents are coping with the changes. She's now taking a whole lot of social cues from you, so if mom and dad are happy and excited about the next move, she will tune into that and likely join in the fun. And the TYPE of change is important here also. Yes, she's leaving her nanny and her house and neighborhood. But she'll be gaining much more access to grandparents, aunts, uncles, cousins and all the warmth and gushing love and excitement that could entail (never mind all the extra support you will get which will, in turn, help you parent with less stress). As you say, the sibling is coming whether she likes it or not. That will be a HUGE transition to deal with and you've thought about this big change deeply. But it actually may be EASIER for your daughter to deal with a new sibling if you do move. Whacky thought, huh? But here's where I'm coming from: Many parents report that the best thing they ever did for the older child to cope with a new sibling is to put him/her in daycare. There, the child gets lots of attention from other adults, she doesn't have to fight mom for her love and affection, and she really feels like she's becoming a "big girl" with a "baby sister" at home. Then when she comes home from daycare, she can have "special time" with mommy while dad takes care of the baby for a while. Your daughter will also have extra access to a bunch of loving adults, her extended family. This may possibly go a long way to buffering the rejection she may feel from mom being with the baby so often.

And here's a crucial point: What WON'T change is mom and dad's love and affection for her. At this age, children aren't as attached to places as they are to their primary caregivers. If they stay stable, predictable, and provide the same love and limits that were set in the old context, chances are they'll adjust quite well in a new place.

#3: What are some practical things to consider if you DO decide to move… I have a few thoughts, but it would be great if anyone else has made a significant move like this one to pipe in with further suggestions.

- Talk about the move with lots of excitement and joy. Plan TOGETHER with your daughter what her new bedroom will look like, how often she'll see grandma, and so on.

- Even if you DO feel lots of anxiety about how she'll cope, don't overly project those anxieties onto her. In other words, you want to let her express her fears of moving, her anger at her new sibling's arrival, her anxieties about not being mommy's little girl, but you want those to mostly come from her. Kids pick up our worries so easily and make them their own, even when they weren't there originally. Open ended questions that provide some choices help if you notice her feeling angry or sad. Something like:  "Are you mad or sad or something else?" Why? Is it because of mommy or daddy or baby?"

- Try to leave yourself several weeks open before you go to work at the new job. So, move several weeks before your mat leave ends. That way, you can put your child into daycare (or whatever arragement you choose) in the next city and deal with any transitional anxieties or behavioural problems before you also have to worry about being on time for work. 

- In terms of sleep specifically, try to mimic the context that she was sleeping in before as much as possible. Go through the same bedtime ritual, play the same music, read the same books, use the same blankets. Put her to bed at the same time and try to enforce those limits as much as possible even though she will surely push on them. This is going to be a time of heightened anxiety and our temptation in these times is often to become more LAX in our rules about sleep. The paradox is that this is exactly when children need us MOST to remain firm, so that they feel like their world is a predictable one, one that can't be shifted easily by the little rages of scared children. They need us to say "everything will be alright, you have to follow this rule, as you always have; we are the big people here and we'll take care of everything."

- Invite lots of family over to your new place early on, even if you're still living in boxes. This will help your daughter realize how great the new move was and how much more love and attention might be hers to enjoy (make sure that you give your family a heads up and ask them to hold and play with your older one as much or more than with the new baby).

#4 In terms of how your daughter will respond, as you can see, it depends on loads of factors and even if you do everything "perfectly" (which doesn't exist), she'll still have normal fears and anxieties that she'll have to work through with your help. Yes, that might entail more tantrums and less sleep. And if you're prepared for this and understand that it's a normal part of adjusting to novelty, it does
n't have to be a horror-filled time at all.

And this bleeds into the unexpressed issue #5: The bottom line for me is that if this job is your dream job and it's also a great location that affords you so many benefits that you look forward to (professionally and personally), then go for it! Your children will adjust, perhaps much easier than you anticipate. And if your daughter does have some difficulties, it's interesting to note that with the very, very rare exception, "biographical memory" doesn't really start until age 3 (in other words, she won't even remember the move by the time she's around 5). I'm partly kidding here (biographical memory does begin usually at around 3, but that's not the point). The point is that you are a thoughtful, engaged, empathic parent who cares deeply for her child's emotional well-being. That will pull her through almost any dramatic transition unscarred and likely better for it.

Good luck and keep us posted on your decision, if you can!