When mom is in her third trimester, she needs to get lots of extra rest. But dads are under no such compunction. If you know you have a baby coming home in a few short weeks, and you know that baby is going to need to be fed every two to four hours, then one of the best things you can do for yourself, your wife, and your baby is to prepare yourself to share some late night parenting times with them.
You can do this by setting a quiet alarm to wake you up every three hours or so through the night. Set it on your side of the bed, and set it low enough so it doesnt wake mom up. When the alarm sounds, resist the urge to hit snooze. Get up and stay up for 15-20 minutes at a time. Then, when baby arrives, it wont seem so difficult to get up when she cries.
Of course, you need to be sensitive to your wife. While this is an excellent way to condition yourself to be able to help with night time parenting, it might also be disruptive to your wifes rest. If you find that mom is having trouble sleeping because you are getting up every three hours, it would be better to go ahead and drop the regimen.
If baby is going to be breast fed, of course, mom will need to wake up for night time feedings whether dad wakes up with them or not. Still, most women find it reassuring and supportive to have their daddy wake up and help however he can. This can include getting up to bring the baby to mom, laying baby back down to sleep after shes done eating, getting mom a glass of water or whatever else she may need, burping the baby, or simply being there to talk and share the experience with mom and the baby.
If your baby is bottle fed, of course, dad can take over some of the night time parenting sessions all by himself. Not only will this give mom such much needed time to rest, but it will allow some wonderful father/baby bonding time.

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