A common question for individuals considering surrogacy is whether the baby will share DNA with the surrogate. The answer depends on the specific type of surrogacy arrangement. Despite a common misconception, in the most prevalent form of surrogacy today, the baby does not share DNA with the carrier.
The Two Main Types of Surrogacy
Surrogacy primarily involves two distinct approaches: gestational surrogacy and traditional surrogacy. These methods differ fundamentally in how the embryo is created and whose genetic material is involved. Gestational surrogacy is the more prevalent method in modern practice, where the surrogate carries a pregnancy conceived using an embryo created outside her body. In contrast, traditional surrogacy involves the surrogate’s own egg being fertilized.
Genetic Connection in Gestational Surrogacy
In gestational surrogacy, the baby does not inherit DNA from the surrogate mother. The process begins with in vitro fertilization (IVF), where an embryo is created in a laboratory setting. This embryo is formed using the egg and sperm of the intended parents, or sometimes from donor egg and/or donor sperm.
Once the embryo develops, it is transferred into the gestational surrogate’s uterus, where she carries the pregnancy to term. Since the surrogate’s own egg is not used, she provides no genetic material to the baby. The surrogate acts purely as the carrier, providing the uterine environment for the baby’s growth and development.
Genetic Connection in Traditional Surrogacy
Traditional surrogacy, though less common today, involves a direct genetic link between the surrogate and the baby. In this arrangement, the surrogate’s own egg is fertilized, typically through artificial insemination, using sperm from the intended father or a sperm donor. This means the surrogate is the biological mother. Because her egg is used, the traditional surrogate contributes 50% of the baby’s DNA, making her genetically related to the child.
Maternal Environment and Other Influences
While a gestational surrogate does not contribute nuclear DNA, her health and the uterine environment during pregnancy can influence fetal development through epigenetic mechanisms. Epigenetics refers to changes in gene expression that do not alter the underlying DNA sequence itself. For example, a surrogate’s diet or stress could influence metabolic pathways or brain development in the fetus, even without changing the baby’s core genetic code. The baby also inherits mitochondrial DNA (mtDNA) exclusively from the egg provider, which is a small fraction of the total genetic material and distinct from nuclear DNA that determines most traits. Although the surrogate’s body hosts the pregnancy, these environmental and minor genetic influences do not alter the baby’s fundamental nuclear DNA received from the egg and sperm providers.