Exercise - even 5 minutes at a time if it is all you have.
Tai Chi. Takes a little time to learn, but worth it.
Relaxation and stretching exercises. Some like Yoga, I just do a generic stretching routine learned partly from Bob Anderson's old book. You would be amazed how tight muscles get without noticing, because you unconsciously go about your business and compensate for the tightening. It creates a feedback loop - tight muscles, unconscious discomfort, stress, more tight muscles...you get the idea. If you can stretch out and loosen those muscles in a healthy manner, maybe several times a day, it can have an amazing effect on reducing the effects of stress. IF you can afford it, a single round of therapeutic massage may help break the pattern.
Finally, meditation. It is easiest to learn it from someone who does it already.
Years ago there was a good book called Yoga Self Taught by Andre Lysbeth (?). Stretching by Bob Anderson is also an oldie that was popular in climbing circles when I got it. Core Performance by Verstegen is a good short exercise routine. What's really good is that none of it can hurt, even if it doesn't exactly do away with all the stress effects. Remember, all this is stress managment, not cure. You have to do it frequently to make it work. One day the cause of the stress will be solved, and it will be better.
I hope you two are okay. Hang in there. It took over two years for our first to be born, and my wife was really stressed. But then again, Sarah in the Bible gave birth in her 90s! Not sure anyone wants to do that today, though...
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Meantime, just keep loving and being kind to each other. That will be most important in the long run.