Does a Gestational Surrogate Share DNA With the Baby?

Short answer: No. A gestational surrogate does not share inherited DNA with the baby simply because she carries the pregnancy. In gestational surrogacy, the embryo is created through IVF using an egg and sperm from the intended parents, donors, or a combination of the two. The surrogate provides the uterus for the pregnancy, but she does not provide the egg.

Where does the baby's DNA come from?

A baby's inherited DNA comes from the egg and sperm that created the embryo. If an intended mother's egg and an intended father's sperm are used, the baby's inherited DNA comes from those two intended parents. If donor eggs, donor sperm, or both are used, the baby's genetic makeup comes from those genetic contributors.

The American Society for Reproductive Medicine defines a gestational carrier as someone who carries a pregnancy created from an embryo produced by genetic parents and/or gamete donors. The American College of Obstetricians and Gynecologists likewise describes the child carried in gestational surrogacy as genetically unrelated to the gestational carrier.

Why doesn't carrying the pregnancy make the surrogate genetically related?

Pregnancy creates an important biological connection between the surrogate and the developing baby, but a biological connection is not the same thing as a genetic relationship. The surrogate's body provides the environment in which the embryo implants and the fetus develops. Through the placenta, the pregnancy receives oxygen and nutrients and undergoes the many physiologic processes needed for development.

Those processes do not replace the DNA inherited when the embryo was created. The surrogate's genes are therefore not added to the baby's inherited genetic code simply because she carries the pregnancy.

Can the surrogate influence the pregnancy without contributing DNA?

Yes. The uterine environment, maternal health, medications, nutrition, infections, exposures and other pregnancy-related factors can affect fetal development. Researchers also study how the pregnancy environment may influence gene expression through epigenetic mechanisms.

That does not mean the gestational surrogate becomes a genetic parent or contributes inherited DNA. It means that, as in any pregnancy, the environment in which a fetus develops matters to health and development.

What about fetal cells and microchimerism?

During pregnancy, small numbers of fetal cells can cross into the pregnant person's bloodstream, and some may persist after delivery. Cells can also move in the other direction. This phenomenon is known as microchimerism.

Microchimerism does not change who contributed the egg or sperm and does not make a gestational surrogate genetically related to the child in the usual inherited sense. It is a separate biological feature of pregnancy.

How is traditional surrogacy different?

Traditional surrogacy is different because the surrogate's own egg is used to create the pregnancy. In that situation, she is genetically related to the child. Traditional surrogacy is distinct from gestational surrogacy and raises different medical, legal and ethical considerations.

If you want to understand that distinction in more detail, read our guide to traditional surrogacy.

Does genetic relationship determine legal parentage?

Not by itself. Genetic, gestational and legal parentage are different concepts. Surrogacy parentage procedures depend on the jurisdiction and the circumstances of the arrangement, which is why intended parents and gestational carriers should work with qualified reproductive-law attorneys familiar with the relevant state or states.

What should intended parents remember?

The simplest way to think about it is this: in gestational surrogacy, the surrogate carries the baby but does not provide the egg. The baby's inherited DNA comes from the people whose egg and sperm created the embryo.

For more information about how the broader journey works, these Expecting.ai guides may help:

• Surrogacy Process in the U.S.: Complete Step-by-Step Guide
• How Are Surrogates Screened?
• What Is Traditional Surrogacy?

This article is for general educational purposes and is not medical or legal advice. Individual treatment and parentage questions should be discussed with the appropriate fertility and legal professionals.