Gestational surrogacy is often joked about from the surrogate’s perspective as “it’s their bun in my oven!,” which really does sum up the process – an egg from the intended mother, sperm from the intended father, and a host uterus to grow and deliver the baby. The gestational carrier has no genetic link with the child she carries, which is seen as one of the chief benefit of the gestational surrogacy process.
Despite the fact that the embryo’s genetic material comes from its parents (or egg/sperm donor), there are ways that the gestational carrier does in fact influence the fetus she carries. Most obviously is in the way she eats, the physical demands of her job and/or lifestyle, the quality of the air she breathes, even the sounds that surround her while she carries the baby. And certainly all of these factors cross intended parents’ minds when they seek out a woman to serve as their carrier, along with her excellent health and good pregnancy and delivery history. Couples understandably want a healthy, stable environment for their child’s first nine months because we know that uterine exposure can have long term effects on a child.
But what about the gestational carrier’s own genetic history? Is that something intended parents should pay attention to?
Conventional wisdom says no, because the carrier isn’t contributing any genetic material to the child. And although that fact still stands, the issue may not be quite as simple as originally thought.
There has long been anecdotal evidence from the egg donor community that perhaps mothers (those who use donor eggs but carry the child themselves) have more genetic influence over their children than initially thought. Parents of children conceived through donor eggs have observed commonalities with some family members, even though the child shares no genetic link with them.
We know from the work of Dr. David Barker (who put forth “The Barker Hypothesis”) that what takes place in the uterus can sometimes be more important than what happens in the home after birth, in terms of genetic expression. He believed that everyday chronic illnesses like heart disease, diabetes, obesity, etc. aren’t always a result of purely genetics and/or lifestyle, but they are influenced by what takes place in the womb during a woman’s pregnancy. This of course corroborates every intended parent’s goal of finding a woman with a very healthy lifestyle to act as their gestational carrier.
But additional research has since been conducted that sought to determine if the gestational carrier (or mother who carries an embryo created from donor eggs) has any influence on the fetus and their genetic expression. After all, her body is supporting the embryo and its development from a very early stage – in some cases, as early as an embryo that’s only eight cells big.
After first studying the embryonic and fetal development of mice, researchers then turned their attention to a group of 10 women, all of whom were carrying a child from a donor egg. The scientists measured the activity of the genetic material that was present in their uterine fluid, and what they found was fascinating.
Present in the endometrial fluid during the time of embryo implantation were multiple micro RNAs, which are the molecules that encode information for how the embryo’s (and ultimately the fetus’s and the child’s) genes will be expressed.
What this means is that it’s the gestational carrier’s DNA (because RNA is a portion of a person’s DNA) that effectively directs the embryo’s genetic development, because RNA affects genetic coding, decoding, regulation and expression. It’s the gestational carrier’s DNA, then, that influences the way the baby develops, because it’s her genetic material that helps determines which of the baby’s genes get turned on and off. The gestational carrier passes these micro RNAs to the embryo via chemical molecules in the endometrial fluid, and it’s thought that they can influence the activity levels of the baby’s genes throughout life.
When considering this impact for mothers who carry children from donor eggs, it can be reassuring and a source of pleasure and pride. Most women are pleased that even though the child is not genetically related to her, her own DNA does exert influence over how the child she carries develops and grows.
This same satisfaction may not be true for couples who use gestational carriers, because it disputes the common wisdom that the surrogate is merely the vessel, and not a contributor to the baby’s genetic expression. While more research is needed to understand the wider implications of DNA, RNA, and assisted reproduction, it’s an issue worth considering when couples choose a woman to carry their baby.
Do gestational carriers or donor egg recipients pass on their DNA to the child they carry? No, it does not seem so (at least as scientists currently understand it). But do these donor egg recipients and gestational carriers effect the expression of the genetics of the child they carry? Yes, reproductive scientists seem to be confirming that fact.
While the current understanding of reproduction and genetics does not yet call for a complete study of a potential gestational carrier’s genetic profile (and certainly the current state of understanding does not offer us any kind of screening mechanism that would be helpful, anyway), intended parents deserve to know the various influences that could impact their baby’s health.
This is definitely an issue worth keeping a close eye on for further developments!