Why does my baby sleep with their mouth open?

She sleeps with her mouth open

We asked this twice, on different nights, in slightly different words. The worry underneath was the same both times: does that mean her nose is blocked?

Sometimes. Often it's just a deeply asleep baby with a slack jaw and nothing else going on.

We stopped looking at the mouth

On its own it doesn't tell you much. What tells you something is everything around it.

Is her breathing easy, or does it look like work? Any snuffling, snorting or whistling from her nose? Nostrils flaring, chest pulling in? What's her colour?

And the one that turned out to be our best sensor: is she still feeding normally. A baby who genuinely can't breathe through her nose struggles to feed, because she can't do both at once. A congested baby who's feeding fine is a congested baby you can leave alone.

The thing we nearly did

We were about to squirt saline up her nose to see whether it came out the other side. Using it as a diagnostic rather than a treatment.

Don't. Saline and suction are for when there's congestion actually getting in her way, not for satisfying a curiosity at midnight. We'd have irritated her nose to answer a question we could have answered by watching her feed.

When we'd mention it

If it were happening every night rather than now and then. If her breathing stayed noisy or snorting. If feeding started getting harder. Loud snoring, or any pause in her breathing.

And any of the effort signs — flaring, chest pulling in, grunting — which stop being an open-mouth question and become a different one.