At the moment, a baby is just that - a baby. A delightful little bundle of joy whose arrival is meant to complete a family. The piece suggests that if people are able to choose the sex of their baby, the situation might change. It might go from the current situation and become a situation where babies are consumer items (ie you can "choose" your baby like you choose a pair of shoes).
Babies might go from just being the result of procreation to being a consumer item.
The process of going from being one thing to being another thing is described as "becoming".
To be honest, they could have just written "... it could lead to babies being consumer items".
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