So for two nights my 16wo DD who usually only wakes twice a night, started waking every 30-90mins after an initial 3hr stretch. The 4 month regression was the first thing that came to mind.
No obvious signs of teething or other discomfort. And she wasn't waking to feed (suckled back to sleep) so don't think it was a growth spurt.
Then last night she went back to her 2 wake ups. I had it in my head that we would be in for a rough couple of weeks. So could the regression have only lasted two nights? Or could it have been something else and was just a taster of what we've got to come?