And I guess it must be very difficult to diagnose in babies that can't tell you what's wrong.

That's right, yes.

So babies don't generally get diagnosed with asthma until they're about four to six years old.

And that's because they can't perform the manoeuvres required to do a lung function test to objectively identify asthma.

But some of my team and others have been looking at doing lung function tests in babies.

So it is possible to look at the lung function of a baby that's six weeks old.

And my colleagues, Jörg Mattes and Adam Collison and Gabriella Martens, have been conducting these studies in babies born to women who've been in my studies of pregnant mums with asthma.

And I imagine if you're having violent coughing while you're pregnant, that's not great.