Can the x-rays penetrate the womb and harm the fetus?

Yes. X-rays can be harmful to the developing fetus, especially in the first three months of a pregnancy. There are usually signs in the x-ray dept telling you to tell the technicians idf you think you could be pregnant. Dental xrays are not a problem as the dental nuse will usually put a lead apron on your tummy before taking them.
Yes. X-rays definitely penetrate the uterus and get to the baby. That's why they always ask if your pregnant before doing x-rays. Most x-rays that you might get are low enough dose not to hurt your baby. High doses of radiation, like for cancer treatment, can cause birth defects if early in pregnancy or increased risk of certain cancers later.