Hamster pregnancies typically last from 17 days (for Syrian hamsters) to 18 to 22 days (in the case of dwarf hamsters). It is not always easy to detect pregnancy in a hamster, but changes in behavior and appearance can give clues as to the hamster's state. If a female hamster begins gathering bedding into a "nest," eating and drinking more or if she gains weight, she is probably pregnant. It is essential to give a female hamster plenty of space during this time period, to prevent her from cannibalizing her young.
Keep her away from crowds and loud surroundings momma hamster need a quite place and dark away from the sun, if you put her outside on bright places or loud places they'll get depress and could eat or kill their new born and also could become stressed and aggrasive
Don't touch her and always keep her bowl full with nutrition like hamsterfood and keep their water bottle full also you can put a few drop of vitamins into their water bottle, I suggest you close her cage with cloth or something so she won't feel threatened by your or someone presence
