My son is 10 months old. He has always slept fairly well (thankfully) but he always has trouble when his mom is leaving. You may be thinking, yeah, he cries when he sees her leave. Nope. He should have no way of knowing.
For example:
When he was born, my wife was working 3rd shift. She was on leave for about 1 1/2 months after he was born but the time came to return to work. At that point in time, he was sleeping 4-5 hours at a time, then he would cry. My wife and I would each take a night to get up with him so one of us could get sleep and he almost always went right back to sleep. The first night she went back to work, I got 20 min of sleep. He cried and screamed the whole night. After that, he would sleep fine when she was home but even though she left 3 hours after he went to bed and she was the one who tucked him in, he would cry a lot more when she was gone.
Now my wife works a different job but leaves in the morning before he gets up. She only works Mon/Wed/Fri for about 4-5 hours a day. On the nights before she has to work (like last night) he cries and will not accept comfort from anyone but mom. If she puts him down, he cries. On nights she doesn't work the next morning, he will maybe wake up once crying but otherwise he is fine. On her off nights, I am also acceptable comfort.
How can he know when she is working or not? We even got to test his knowledge by messing with the days a little. One week, she switched days and worked Tuesday instead of Monday. He followed along and cried Monday night. Sunday night was fine. The next week she took off on Friday. He was fine Thurdsay night.
