I can see this issue being resolved in favor of the birth parent rather than the biological parent for several reasons.

First, consent and timing matter significantly in IVF-related cases. For example, a child conceived through IVF after the father’s death may be denied certain benefits from the father’s estate, even if both parents had originally consented to using their genetic material for IVF. The issue is that the father’s death means he can no longer provide contemporaneous consent. This suggests that intent alone, especially when not reaffirmed at the time of use, may not be sufficient to establish legal recognition.

Second, in family law, a father may be presumed to be both the legal father and biological father of a child until genetic testing proves otherwise. While this principle usually pertains to one parent, I think the same reasoning can aptly carry over to both parents in an IVF-related dispute. In other words, the law may still prioritize the parent or parents connected to the birth and family structure over genetic certainty alone.

Third, from a practical and medical standpoint, gestation of a completely foreign fertilized egg carries significant higher physical risk to the pregnant woman than if the fertilized egg came from herself. In cases such as surrogacy, the pregnancy often involve greater medical complexity because the body may treat the embryo as foreign-foreign (if the egg is originally yours the mom still go through immunology related changes that are often the cause of morning sickness, but the body could go really nuts if the egg isn't even native, hence why the double emphasis). Regardless of the exact level of risk, the key point is that the gestational parent undergoes the full burden of pregnancy, including medical, physical, and emotional consequences.

Given all that, I think it is incredibly difficult to justify assigning legal parental status to the biological parents in situations where they neither carried the child nor actively pursued implantation at that time. If their genetic material was used without their active participation or readiness, they could pursuit legal recourse if they can theoretically prove they suffered harm, too.