Vitamin D drops...

It honestly doesn't matter that you have missed a week. I was never good remembering to give them to my first, I'm slightly better second time round, but probably still miss a couple days a week. Don't beat yourself up. Just try to start now and if you forget give yourself some grace. Xx

Preface my experience and opinion only........

I didn't start until week 4, but that's because I was just in the throws of being a new mum and i forgot not because that was the recommendation.

Didn't hurt (so far) its to assist development apparently they don't get as much vitamin D as a breastfed child as they would if they were on formula.

I'm not sure about long term but the way I look at it is that however many years ago people didn't give kids things like that, so I'm sure its fine, but get into the habit.

I give my little boy the drops when I remember which is usually his pre-bed feed but I know I don't always remember! I doubt missing a week will hurt x