Went to baby clinic this afternoon to get the babies weighed and talk to the health visitor about A not smiling. It was my first solo trip to the clinic but E and A were very good - Esme only screamed a little bit when she was weighed (they have to be naked - something neither of them are that keen on), and A didn't let out a squeak when I undressed him, weighed him or dressed him. Unbelievable!
After getting them weighed I was waiting around to speak to the health visitor. Both babies were fussing a little bit, so I was holding E and the healthcare assistant offered to hold A. While she was holding him I was chatting to her about him not smiling so she made some faces at him and he prompted smiled three times in a row! How stupid did I feel? So thank you very much A for making your mum look like a total fool! I had spent the whole day really making sure I made loads of eye contact with him and smiling lots and lots (my face is aching), as I realised that often when I talk to him I mirror his facial expressions. So there was no more mirroring from me today, just lots and lots of smiles and it obviously worked.
After that I decided not to wait around for the health visitor - if the smiles don't develop over the next week I'll go back to talk to her, but hopefully there'll be no need.