File as Married Filing Jointly and include an Injured Spouse Form 8379 with your tax return.
See this TurboTax support FAQ on filing a Form 8379 - https://ttlc.intuit.com/questions/1910698-how-do-i-file-form-8379-injured-spouse-allocation
Did you ever file these back taxes?
<a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/3026629-i-forgot-to-file-my-taxes-for-2015">https://ttlc.intuit.com/questions/3026629-i-forgot-to-file-my-taxes-for-2015</a>
So did you file Married Separately yourself those years? Which state do you live in?
We've only been married for 1 year and last year we filed separately but I recently gave birth to our daughter and was wondering if it'd be better to file jointly or separately?
Follow the instructions in the answer below. If you live in a Community Property State, though, it may be of limited use.
File as Married Filing Jointly and include an Injured Spouse Form 8379 with your tax return.
See this TurboTax support FAQ on filing a Form 8379 - https://ttlc.intuit.com/questions/1910698-how-do-i-file-form-8379-injured-spouse-allocation