Hello there, I wish my answer should provide you insight to the problem.
First.She is in her first month and as you said she has small
cerebellum,it is an anomaly and could lead to symptoms particularly of imbalance in upcoming future. But how and to what extent it will all unfold is difficult to define.I would also add that children do have a great potential to recover.So we will have to wait.
Second,It is not always possible to detect all functional abnormality in brain and other organs because the fetus is developing during
pregnancy.
Third , calcified cerebellum.Really, it can occur when we have such problem.But again it does not defines to what extent it could be pathological in giving symptoms.
Finally,we do not have the clear diagnosis until now we are just assuming consequences what will happen.It might be due to hypoxic
injury or any other forms of congenital developmental anomaly.So it is better to visit a
pediatrician first and also seek opinion from pediatric
neurologist.
I hope that the above said statement will provide you the best knowledge needed to get through your difficult period and help you stop worrying.