Still no babies

I've had my rats together for about a month now and the female still isn't showing any signs of pregnancy. Is there a trick to it?

How old are they did you purchase young rats and raised them up or did you purchased adult?

Reason I am asking is that if you purchased adults the female could very well be an older female at the end or her reproduction life.

Could be other things

Do you have more than 1 male and one female?

If you only have 1.1 your male could be unfertile.

They could be too young.

Etc there can be various reason why they have not produced yet, since you do not give any details it's hard to tell.

I can tell you that I usually have babies within 3 to 4 weeks once paired even with first time breeders.

I have 1.1 and they seemed young when I got them. the male has gotten bigger and I think the female has to. I don't know how old they were seemed sort of young. I would get another from the same pet store bit it's an hour away, would petsmart be a good place to get a female?

I put 4 to 5 week old rats in groups and rarely get litters before 10 wks old, usually at 11 or 12 weeks old or older.