The risk to your baby from
hydrocodone is very, very low-- if there is any risk at all.
Opioids are not 'teratogenic'-- they do not cause birth defects-- but the poor diet and repeated withdrawal often associated with opioids are not good for the baby, or for you. Frankly, if you can continue taking the same 3 tablets of hydrocodone throughout your pregnancy, the risk would be minimal. But most OB's would likely prefer you stopped them, as you probably already know.