Is diagnostic testing worth the risks?

Absolutely !!! As long as it is being done by a board certified obgyn or peri-natologist why would u want to take a chance and not know if something is wrong with your baby because if something is u are better off knowing as it could affect what u do with the pregnancy or what type of delivery is best or if somehting is wrong( hopefully not and it is reassuring to know it is not) your baby may need immed care.
Yes. This is definitely not a straight forward yes/no answer. Whether or not the risks of any diagnostic test are 'worth it' is entirely up to you. It depends on how important a definitive answer is to you and what you would do with this information.