If I had my pregnancy pack with me I would look in it and get the sheet of information. Apparently this swab is what most women get, it is to see if you carry some sort of infection or something?

here you go - http://www.birth.com.au/Info.asp?class=6625&page=11

I was told by my Midwife that they will be collecting that swab from me at 36 weeks and also at that appt I will see a doctor and get my scan to estimate how big the baby is. But not all women get this of course as every doctor and midwife is different. I know my cousin never got a scan at 36 weeks, or at all to estimate the size of the baby.