Broody or not this time of year is not a good time to have little babies....too darn cold. Unless you "want" to have babies and can provide a dry, warm place for two to three months....like inside your house....uuuugh !! Been there, done that....not fun ......
I never had a broody hen during the Winter and if I did, I would take the eggs away everyday so she wont try to stay broody.
A hen can sit on as much as 12 eggs at a time but chances are they will not all survive because there isn't enough consistent heat from the Hen to keep the embryo from completely forming.
I usually keep 6-8 eggs under my broodey hen.
. If she is Broody, she will get very up-set with you if you try to remove the egg from underneath her and she will peck at your hand. She will squack at you.
A broody hen will also not leave the nesting box accept to eat and drink and defecate which is only 1/2 hour to an hour a day. She will continually sit for 23 hours a day....
If she leaves the nest for more than a couple hours and leaves the eggs un-attended, they will not survive unless another hen takes over.
It's really hard to keep track of who is laying on the eggs and if the broody hen is leaving for long periods at a time. The best way to see if a egg is actually fertile is to candle the egg at about two to three days after a hen has sat on them. It's better at a week to two weeks to see growth inside an egg.
Do you have a Rooster ?