How Surrogacy Works
Surrogacy provides a pathway to parenthood for individuals or couples who are unable to carry a pregnancy themselves. This process involves another woman, the surrogate, carrying a pregnancy for the intended parents. There are two primary forms of surrogacy, each differing significantly in how the pregnancy is established and, consequently, the genetic relationship to the child.
Traditional surrogacy involves the surrogate mother using her own egg, which is then fertilized. This fertilization typically occurs through artificial insemination with sperm from the intended father or a donor. In this scenario, the surrogate contributes both the genetic material from her egg and the uterine environment for the developing embryo. This method establishes a direct biological link between the surrogate and the child.
In contrast, gestational surrogacy is a more common approach today. This method involves creating an embryo using in vitro fertilization (IVF) with genetic material from the intended parents or donors. The pre-formed embryo is then transferred into the gestational surrogate’s uterus. The gestational surrogate provides the uterine environment for the embryo to implant and grow, but she does not contribute any of her own genetic material to the child.
DNA in Traditional Surrogacy
In traditional surrogacy, the surrogate mother is the biological mother of the child. This means she contributes half of the baby’s genetic material through her egg. This genetic connection is comparable to that between any biological mother and her child.
DNA in Gestational Surrogacy
Gestational surrogacy operates differently regarding genetic inheritance. In this process, the embryo is created outside the surrogate’s body using an egg and sperm from the intended parents or from donors. This embryo, containing the complete genetic blueprint, is then transferred into the gestational surrogate’s uterus. The gestational surrogate’s role is to carry the pregnancy to term, providing the necessary environment for fetal development.
The gestational surrogate does not contribute any genetic material to the baby. The nuclear DNA, which dictates traits like eye color, hair color, and many predispositions, comes entirely from the egg provider and the sperm provider. Furthermore, mitochondrial DNA, inherited exclusively from the egg provider, also does not come from the gestational surrogate.
This means that a baby born via gestational surrogacy will have no genetic link to the woman who carried the pregnancy. This distinction is fundamental to understanding the genetic outcome in gestational surrogacy.
Beyond DNA The Surrogate’s Role
While a gestational surrogate does not contribute any DNA, her biological role in the development of the baby is still significant. She provides the entire intrauterine environment for approximately nine months. This includes supplying nourishment, oxygen, and protection to the developing fetus through the placenta and umbilical cord.
The uterine environment plays a role in fetal growth and health, influencing how the baby develops over time. Factors like the surrogate’s nutrition, health, and lifestyle during pregnancy can affect the baby’s prenatal development. This influence, however, is environmental and does not involve the transfer of genetic material. The surrogate’s body acts as a vessel, nurturing the genetically distinct embryo until birth.