That's precisely the reason why traditional surrogacy arrangements are not carried out anymore. If a woman is the biological mother of the child in addition to the birth mother, the emotional attachment will be stronger.
In gestational surrogacy, inversely, even though it's only logical that you build a tie with the child anyway, it also develops with the intended parents: surrogates feel happiness for the intended parents, hence that they build a lifelong relationship throughout the 9 months of pregnancy. This translates into love not just for the child, for for the new family as well.
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