Surrogacy is an arrangement where a woman carries and gives birth to a baby for another couple or individual. The surrogate mother agrees to become pregnant and carry the pregnancy to term with the intention of handing over the baby to the intended parents once it is born. Surrogacy can be a wonderful option for people who are unable to carry a pregnancy themselves but want to have a baby that is biologically related to them. However, it also raises a lot of questions, including whether the baby takes on any of the surrogate mother’s DNA during gestation. In this article, we will examine the science behind how a baby’s DNA is formed and discuss what impact, if any, a surrogate mother has on a baby’s genetic makeup.
How is a baby’s DNA formed?
A baby’s DNA comes from the sperm and egg that created the embryo. At the moment of fertilization when the sperm and egg meet, the DNA from the biological father and mother combine to create a new unique genome for that child. This means that the baby’s DNA is set right from the start and does not change based on who carries the pregnancy.
More specifically, here is how a baby’s DNA is formed:
- The biological father’s sperm contains 23 chromosomes, with half of the father’s DNA.
- The biological mother’s egg also contains 23 chromosomes, with half of the mother’s DNA.
- When fertilization occurs, the sperm and egg fuse together, combining 23 chromosomes from each parent for a total of 46 chromosomes.
- These 46 chromosomes make up a baby’s full set of DNA with genetic information from both the biological mother and father.
This process happens the same way whether conception occurs through sexual intercourse or through in vitro fertilization (IVF) as is the case with surrogacy. With IVF for surrogacy, the egg and sperm that create the embryo placed into the surrogate mother still determine the baby’s DNA.
Does a surrogate mother’s DNA impact the baby?
Given that a baby’s DNA is set at the moment of conception, a surrogate mother’s own DNA does not impact the genetics of the child she is carrying. The surrogate does not contribute any of her own DNA to the baby.
However, there are some indirect ways that a surrogate mother could potentially impact attributes of the developing baby through epigenetics and the uterine environment:
Epigenetics
Epigenetics refers to changes in gene expression caused by mechanisms other than changes in the underlying DNA sequence. Environmental influences like diet, stress, toxins etc. can cause epigenetic changes by essentially turning certain genes “on” or “off.” These changes do not alter the DNA code itself but can impact how the genes are expressed physically.
Some epigenetic changes in a surrogate mother could theoretically be passed onto the developing fetus in utero and persist after birth. However, the impact of any such epigenetic changes is expected to be very small compared to the influence of the baby’s inherited DNA.
Uterine Environment
The conditions inside the uterus during pregnancy can also impact fetal development. The surrogate mother’s diet, lifestyle habits, and overall health influence the nutrients and environment the baby is exposed to in the womb. These factors are known to affect outcomes like birth weight and risks for certain diseases later in life.
However, these uterine environmental influences do not change the baby’s fundamental DNA makeup or genes. The developing baby is still very much the biological child of the egg and sperm donors.
What about mitochondrial DNA?
Mitochondria are small structures found inside most cells that produce energy for cell functions. Mitochondria have their own DNA separate from the 46 chromosomes that make up our main DNA. Mitochondrial DNA comes only from the biological mother, transmitted via the egg at conception.
In traditional conception, the mitochondrial DNA comes from the woman who provides the egg and carries the pregnancy. But in surrogacy, the egg donor is the genetic mother contributing the mitochondrial DNA, not the surrogate. So the surrogate mother’s mitochondrial DNA is not passed to the baby.
Can a surrogate mother’s DNA show up in the baby’s results?
Given the above, a surrogate mother’s DNA should not be detected in genetic testing of a newborn she carried. There are some rare exceptions where small amounts of the surrogate’s DNA could be picked up:
– **Microchimerism -** Pregnancy sometimes results in cross-over of a very small number of cells between mother and baby. A few cells with the surrogate mother’s DNA may pass to the baby in the womb and persist after birth. These are unlikely to impact the baby’s health or development.
– **Contamination** – If the surrogate mother’s DNA somehow contaminated the baby’s genetic sample during collection or processing, it could skew test results. But contamination is usually identifiable and would not reflect the baby’s actual DNA profile.
Aside from these rare situations, the baby’s genetic results should match the egg and sperm donor without indicators of the surrogate’s DNA. Proper precautions during sample handling help avoid any contamination.
Summary
In summary, a surrogate mother does not transmit her own DNA to the developing baby. The baby’s genetic identity is set at conception based on the egg and sperm. A surrogate may have minor indirect impacts through epigenetics or uterine conditions, but she does not contribute to the baby’s actual genetic code or profile. While exceedingly rare cases of microchimerism may result in traces of the surrogate’s DNA, this does not amount to meaningful genetic contribution to the child. Genetic testing of the newborn should reflect only the DNA profiles of the intended biological parents.
Conclusion
Based on our understanding of genetics and reproduction, a surrogate mother does not transmit her DNA to the baby she carries. The baby’s genetic makeup and profile is determined by the biological mother and father who contributed the egg and sperm. Surrogacy simply provides an alternative route for conception and gestation when needed, but the surrogate herself does not impact the fundamental genetic identity of the child. Genetic parentage remains with the providers of the egg and sperm used to create the embryo transferred into the surrogate. While further research may reveal more about non-genetic influences on development in utero, a surrogate mother’s direct genetic contributions are virtually nonexistent given how human DNA is established at the time of fertilization.