How long did your LO's 4 month regression last?
If you were lucky enough to escape it,
M's was about 2.5 months long of hourly wake ups. She was a crap sleeper to begin with so it only got worse. But at the end of it at 7.5 months she started STTN. And then at about 10.5 months she started waking up again. Yippee.