Lenin I don't think you need to wait until you've had a period. My GP was happy for me to have a smear at 7 weeks post-partum. It actually took me about 6 months to get around to it <blush> and by that time I had just started getting periods again.
They like to have a smear from the middle of the month because that's when the chances of getting a successful smear are highest... but if you're not having periods it shouldn't matter. According to my GP any way
The hormone levels change the maturity of the cervical epithelium. At mid-cycle the oestrogen levels are higher and the cervical cells at their most 'mature' and this is about the 'easiest' presentation to read by the cytologist. Postnatal can be tricky because the cells are less mature. The less maturity = cells with higher nucleus to cytoplasmic ratio; this has some degree of overlap with a change we look for that indicates abnormality. The more abnormal a cell is, the less it differentiates, i.e. doesn't obey the usual hormonal influences. We can tell the difference (usually anyway) between immature epithelial cells due to hormonal status* and abnormal changes, it's occasionally quite tricky. So it's preferable to leave a Pap test until the hormones are nearer to normal status, usually we ask after 12 weeks. Bf shouldn't be a problem but *it is jolly helpful if the sample taker puts the info on the request form.