When you get married the debt you have amassed prior to the marriage do not automatically become the liability of your new spouse. However, the new spouse has to be careful to make sure that they do not become liable for the debt by using your credit card, becoming a joint user of the account; promising to satisfy the debt, or otherwise creating an obligation that does not exist.
Many States require spouses to be liable for debts that their spouse has regarding housing, food or medical expenses. There is a chance that these types of essential debts will create liability for the new spouse.
If you file bankruptcy before you get married there should be little to no effect on the spouses’ credit report. If you share an address and/or a last name before you get married negative information can migrate to the significant others credit report but this can be removed.
If you file bankruptcy when you are married it is likely that the negative information could get to the spouses credit report and this should be monitored. If you are a co-signor on debt then the bankruptcy will most likely if not definitely end up on the other guarantors report.
Disclaimer: This answer does not constitute legal advice. I am admitted in the States of New York, New Jersey and Massachusetts only and make no attempt to opine on matters of law that are not relevant to those three States. This advice is based on general principles of law that may or may not relate to your specific situation. Facts and laws change and these possible changes will affect the advice provided here. Consult an attorney in your locale before you act on any of this advice. You should not rely on this advice alone and nothing in these communications creates an attorney client relationship. The opinions expressed herein are those of the author only and the fact that he has worked as an Assistant District Attorney; State Supreme Court Clerk; Special Assistant United States Attorney (Hawaii); Assistant Cornell University Counsel or Judge Advocate, United States Marine Corps should not be relied upon to assume that these statements reflect the policy of these organizations.