DS3 will be 20 weeks old on Monday. Up until one week ago he was exclusively breastfed. During the last week he has had about 12 ounces of formula, in addition to breast milk.
He is quite big (91st centile) and seems very discontented at the moment. He seems incapable of sleeping longer than two hours at the very most, whereas up until recently he was going in his cot at 8 p.m. and sleeping until 12 or even 1 a.m. Now I often cannot get him to go down in the evenings at all, and am breastfeeding him three or four times between 11.30 and 6 a.m. His daytime naps have become very patchy too (whereas we were previously in a routine of short nap in the morning, long nap after lunch, short nap in the late afternoon).
He hasn't had any bad reaction to his three bottles of formula (no rash, no vomiting, not too windy etc).
He is clearly very interested in the food we are eating - he sits at the table with us and watches us and licks his lips! He tried to grab a bit of banana from me yesterday, and lunchtime today tried to mug DS2 for a piece of toast.
DS1 and DS2 started on solids when they were 16 weeks with no discernible ill effects - DS2 was pretty porky, but then he was chubby before he started on solids so I don't know whether it made any difference. DS1 did have eczema but I think that was caused by formula (which I introduced much earlier with him) rather than by solids.
So what are the arguments in favour of leaving it any longer to start him on solids?