A couple more things about naps:
Circadian rhythms and ?sleepy times? of day around 9am and 1pm ish don?t get going till 3-4 months (later for some babies, especially those who had colic) as the LO?s biological clocks need to mature first. It?s not till around 10 months on average that babies? body clocks are fully synchronised with the 24 hour day.
Before that point, keeping awake intervals short is the key to naps. A maximum of 1.5 hours is a good rule of thumb, although it varies from about 45 mins ? 2 hours. Awake times usually get longer as the day goes on, so a baby who can only stay awake 45 mins between waking for the day and the first nap may be able to go 1.5 hours between the last nap and bedtime. This pattern continues.
Nap length can tell you quite a lot. Once you get past the newborn stage, naps of less than 30 minutes don?t really count as naps ? they take the edge off the tiredness, but don?t really have a restorative effect & don?t bring down cortisol levels properly. So the effect of a 20 min nap is the same as missing that nap altogether.
Babies come into light sleep after 15-20 mins, so a baby waking at that point may need help to stay asleep ? usually from whatever means you used to get them to sleep in the first place. My DS does this for car / sling naps ? he wakes at this point if the car / sling is no longer moving. He?ll never go off again ? you need to have the movement already going when you hit that point. In his case, I suspect it might be to do with being upright, as he does it if he?s sleeping on your chest while you sit in a chair. It doesn?t happen when lying down in the pushchair or his cot.
30 min naps are often due to overtiredness from being awake too long, although they can also be caused by a developmental spurt, or when a baby is almost ready to drop a nap. 40-45 mins is usually one sleep cycle for a nap. If your baby wakes after 30-45 mins and can be got back to sleep by rocking / feeding / whatever, the issue is an inability to settle themselves between cycles, not overtiredness.
gaelic, if I were in your situation and things didn't improve a bit once your new back-at-work routine gets established, I'd consider getting specialist help from someone like Millpond clinic who have a decent understanding about sleep disorders. I do think she is at the extreme end of sleep dificulties, although I'm no expert.
Have you ever had her checked for allergies? I know they can sometimes affect sleep badly.