Not to be a stickler, but although the risk is relatively moderate in general with all of these things, I believe pre-packaged meats are also advised to be avoided. I think these are classified as 'luncheon meats' as distinguishable from 'deli meats' which seem to be those behind the counter. Unfortunately listeria can enter pre-packaged meats before packaging, and can survive even in little or no oxygen (vacuum packaging) so the risk is still there.
At least that's how I interpretted it: https://www.cdc.gov/ncbddd/pregnancy_gateway/infections-listeria.html
https://www.marchofdimes.com/nutrition_risks.html
I think the advice is different in different countries. I rechecked the information given by the midwife and it doesn't say anything about not eating packaged meat.
I checked the NHS website https://www.nhs.uk/chq/Pages/917.aspx?CategoryID=54&SubCategoryID=130 which says in the UK they do not advise you to cut out cold meats. I think it is to do with the risk factor of contracting it is low here? The NHS website also states there was only 156 cases of contracting listeria in the whole of UK in 2010.
It has kind of put me off ham sandwiches though, maybe i will stick to tuna or cheese!