Yes a mother can pass cancer from herself to the baby during the pregnancy.
However it's really extremely rare that a baby gets cancer from the mother during pregnancy.
There have been several mothers who had cancer and got pregnant and gave birth to a happy, healthy baby that never developed cancer.
Sometimes the baby may develop cancer later in life as they get older but that's also rare.
So you're usually safe to give birth to a baby or get pregnant when you have cancer and the baby will usually be just fine.
But I personally would not want to give birth or get pregnant when I had cancer unless I fully cured of it just to prevent the possibility of the baby getting cancer or the possibility of me dying and the baby being without a mother.