I don't believe this. But may be just if you have a good relationship with your 99, then emotionally you have one more people to support you rather than against you. Emtion can affect you physical heath ma.
To be honest, even not for give birth, just for normal live, if you have good relationship with 99, your life will be much easier. But in reality, this is not controlled by us, as many 99 are very bad to us !