Board Thread:Boruto Discussions/@comment-5085906-20170430152255/@comment-3568954-20170518121808

there is no way anyone in the leaf would take the chance of sealing a biju back into kushina, if the jinchuriki dies, the biju also temporarily dies until its reborn however long later. so even if minata that there was a possiblity that resealing kurama into kushina would save her life, he wouldn't have taken the chance of not only losing kushina but losing the biju. so the only logical thing was to seal the biju into naruto.

even if he did seal kurama back into her she still just went though child birth and as such her body would have still been beat up from the child birth and her chakra network would have still been weak and as such kurama could have still been unsealed again.

there is also the possiblity that the only reason resealing kurama worked on naruto in the first place is because naruto is a transmigrant of asura and as such has a far stronger life force than anyone else