Unfortunately, this is difficult situation here because no one really can predict the future, especially with a 19 week old fetus.
When they say that there is an issue with L2 and L3 and kyphosis -- it appears that the spine itself did not form correctly at this level, which can be an issue related to "spina bifida".
Unfortunately, at this time, it would be impossible to know if the nerves themselves were formed correctly, and if they would be functional below this level in the spine.
If the nerves did not function -- this would mean minimal movement in the hips, but no movement in the lower legs, leaving someone without the ability to walk, have sensation in the legs, or have bowel or bladder control. And that is an IF -- IF the nerves did not work below this area.
Surgeries can be done to "fuse" any abnormally formed bone -- but surgeries do not reverse nerve injuries, and that is what cannot be predicted. And they won't be able to predict what will happen as the pregnancy progresses.
So it is a tough decision, and one that can only be made after considering the risks and benefits and potential disability that this child may face during their lifetime.