You do not say what type of hamsters you have.
If they are Syrian (teddybear, standard, golden, fancy) then the gestation
period is 16 days. They rarely go over this but occasionally can go 17-18 days
before giving birth. Syrians can have phantom pregnancies and so your hamster
may not really be pregnant, just look it. Sometimes there can be problems
giving birth and females have the ability to absorb babies back into the blood
stream. You need to keep an eye on your female and if she appears to be in
distress at all seek veterinary advice.
If they are Dwarf Hamsters (Russian, Chinese) then the gestation period is
18-21 days and so the litte will probably be born soon.
You also say you recently separated the male and female. If your hamsters are
Syrian they should be living separately as they are solitary animals and will
not tolerate the company of another once mature. If they are Syrian it would
suggest that your female is very young and therefore will need lots of extra
care whilst nursing to avoid cannabilism of the litter.
If they are Dwarf Hamsters the male will help with the rearing of the litter
and should ideally be left with the female. This of course will mean that they
will breed again and you may not wish for another litter. But if you do intend
for them to breed again the male should be placed back with the female as to
leave him out for too long could mean you cannot re-introduce him at a later
date.
Lorraine
The Complete Hamster Site
http://www.hamsters.co.uk