If you are considering IVF with donor eggs, you are already on a long and complicated road to becoming a parent. You are not alone, as infertility affects millions of women, but sometimes the hurdles along the way seem insurmountable. We want to help by providing the information you need to decide if IVF with donor eggs is right for your family.
Women who are thinking about using donor eggs want to know if the baby will resemble them. The reality that your partner’s sperm will join another woman’s egg brings up all sorts of questions. You may be wondering:
- Will the baby look like me?
- Will the baby act like me?
- How can I bond with the baby?
Genetics research is rapidly advancing, and many commonly held ideas about heredity have been proven false. In fact, heredity is much more complex than previously thought. With information from recent research studies, we can provide you with the most up-to-date material to assist in your decision.
We know that genes determine inheritance of appearance, but the specifics are complex. Physical traits are inherited for everything from eye and hair color to blood type and Rh factor. In addition to these physical traits, there are other inherited characteristics, like personality, IQ and talents. All three people involved (egg donor, egg recipient and egg recipient’s partner) affect the growing fetus in different and significant ways, and the odds that a baby will look like any of them varies.
An egg recipient is not just an “incubator” for the baby. She is the mother and she provides everything the fetus needs to grow and develop. Licensed Clinical Social Worker Lissa Kline, who is Director of Member Services at Progyny, summed it up for an article in Psychology Today:
“The shape of the baby’s earlobe may have been genetically programmed by the donor’s great, great, grandfather, or the male partner’s (or even sperm donor’s) grandmother’s aunt, but the earlobe itself, and the rest of the baby, grew from the pregnant woman’s body. She may not be a genetic donor but carrying the child makes her the child’s biological mother”1
Licensed Clinical Social Worker – Lissa Kline
Here’s the short answer to the overriding question:
Yes, an egg recipient mother influences the development of an embryo created from a donor egg. How does this happen? Let’s explore.
Genetic Inheritance of Appearance and Donor Eggs
Each baby’s physical composition is determined by genetics. When couples use a donor egg, the genes of the egg donor and egg recipient’s partner combine and establish some undeniable traits. Common examples of traits that are passed through the generations are: ear lobe attachment, tongue rolling, freckles, dimples, handedness and red/green color blindness. The egg recipient will have no effect on these characteristics, as they are hard wired in genetic code.
However, current scientific information suggests that genetic inheritance of appearance goes well beyond the simple, outdated notion that dominant and recessive genes can only produce finite variations. The combinations are literally endless.
How are traits passed down through the generations?
Each human has a unique genetic code. The building blocks of this code are known as deoxyribonucleic acid (DNA), and a long string of DNA is the blueprint for that particular person. For each human trait, there is a gene (or cluster of genes) that influences that trait. When egg cells and sperm cells combine, the individual DNA from each creates a new human with traits from both mother and father.
In order for traits to be passed from one generation to the next, the cells must go through a translation process. It is fairly complex, but the simplified explanation is this: a gene’s DNA sequence is converted to ribonucleic acid (RNA) which carries a message for the material to convert to proteins. This is known as gene expression. The way that the DNA is ultimately decoded and converted into protein determines how the gene expresses itself, or appears, in the baby.
You may also be interested in watching #IVFANSWERS episode: Epigenetics – do babies end up looking like the egg recipient?
When elements of genetic code combine, the genes follow some basic principles of inheritance, first identified by scientist Gregor Mendel in the 1800s:
- Law of Dominance
- Law of Segregation
- Law of Independent Assortment
These laws explain the basics of genetics that you probably learned in science class in high school: dominant genes suppress recessive genes. After years of research, we now know that it’s not that simple. There are all sorts of variations in gene expression, so we cannot definitively predict how a gene will express itself in offspring. This means that simply because mother and father both have blue eyes, we cannot state with certainty that the baby will also have blue eyes.
The specifics of passing genetic characteristics from parent to child can best be described, visually, with a graph known as a Punnett Square. The diagram is used to predict the probability that a child will inherit a specific trait. Humans contain two copies of each specific gene. For each trait, one allele from the mother combines with one allele from the father, resulting in many possible variations of gene expression in the offspring. Where it gets tricky is that we now know that traits are usually determined by more than one gene, meaning that the original, simple Punnett Square is oversimplified and cannot tell the whole story.
To further complicate the laws identified by Mendel, we look to the idea of epigenetics. The term’s literal meaning is: “in addition to changes in genetic sequence.” What this means on a practical level, is that heredity is determined by more than just DNA sequence. Epigenetics tells us that gene expression may also be influenced by matter other than its alleles. For couples considering IVF with donor eggs, epigenetics suggests that the baby may or may not look like a combination of the egg donor and the egg recipient’s partner; there are too many variations and unknowns to make that prediction. The baby may strongly resemble, moderately resemble, or share no resemblance to the egg donor, egg recipient or egg recipient’s partner.
Which traits are inherited from the egg (oocyte) donor?
The baby’s basic genetic code is inherited from the egg donor and the egg recipient’s partner. This means that everything from eye color to adult height to blood type is determined their genes. However, this does not mean that the baby’s eye color will be a combination of simple dominant/recessive elements of the egg donor and egg recipient.
Consider this example: the egg donor has blue eyes and the egg recipient’s partner has brown eyes. What color eyes will the baby have? The outdated simplistic nature of dominant/recessive gene theory says the baby will have brown eyes. However, we know that there are actually numerous combinations for eye color, because we cannot definitively predict how the genes will be expressed. The baby’s eyes could be brown, blue, green or even combination of colors.
Which traits are inherited from the egg recipient and her partner?
The egg recipient’s partner is responsible for 50% of the baby’s genetic code, but what role does the egg recipient play in the baby’s appearance and development? While the baby does not directly receive DNA coding from the egg recipient, recent studies suggest that the recipient’s DNA does influence how the baby develops.
The scientific community is not in complete agreement, but studies suggest (and new studies are underway) a new hypothesis that the egg recipient does have a genetic role in inheritance.
“The Fundacion Instituto Valenciano de Infertilidad, a non-profit research center for reproductive health, and Stanford University have concluded that microRNA’s molecules secreted in the mother’s womb are capable of changing the genetic information of the developing fetus.” 2
Los Angeles-based neuroscientist Helder Filipe says scientists discovered that certain microRNAs were expressed in the uterine lining and appeared in the endometrial fluid. These micro RNAs affect gene expression, which means there is evidence that the baby can receive certain genetic inheritance from the egg recipient.
“The idea that the uterine environment can change gene expression in the embryo seems valid and not much of a surprise. This study just reveals a possible mechanism for that change – that’s worth being considered,” Filipe said. 2
In addition, the egg recipient affects how genes are expressed through her health and lifestyle choices. Nutrition is critically important to the creation of uterine lining and forming the placenta. For example, a fetus may be genetically predisposed to be extremely tall. However, if the egg recipient has poor nutrition and prenatal care, the “tall” genes may not receive the nourishment they need to fulfill the destiny of height.
How Does Genetic Inheritance Affect the Appearance of the Baby?
In other words: who will the baby look like?
Some of the most common questions about inherited appearance concern these traits:
- Eye Color
- Hair Color and Hair Structure
- Skin and Complexion
- Blood Type and RH Factor
The pigmentation of the iris is responsible for eye color. A specific pigment called melanin determines the color of the iris, with possibilities ranging from very light blue to extremely dark brown. More melanin means darker eye color. Depending on how the genes express themselves, the amount of protein present in the cells controls how much (or little) melanin exists. The variability of the amount of protein explains why we cannot rely on the outdated studies surrounding dominant and recessive genes to determine eye colors. Multiple genes are involved, which means multiple color possibilities exist. 3
The two genes linked to eye color are OCA2 and HERC2. They both have different versions (alleles), which represent brown color (O and H) and blue color (o and h). The reality is actually quite complex, but the simplified explanation is that between the mother’s and father’s genes there are 9 possible genetic combinations:
Have you ever wondered how blue-eyed parents can produce a brown-eyed baby?
The two different genes (OCA2 and HERC2 must work together to determine eye color. These genes need each other to function properly and produce the more common color, brown. When one or both of these genes are “broken,” little or no pigment is produced and the baby will have blue eyes. Because the genes must work together, it is possible for both blue-eyed parents to be carriers of the dominant brown color trait and produce a child with brown eyes. The illustration, below, describes the different outcomes when the two genes work together and when they do not. 4
Hair Color and Hair Structure
Similar to eye color, the amount of melanin determines hair color. In addition to the amount of melanin present in the cells, the type of melanin is also a factor. Two types of melanin that create hair color are eumelanin and pheomelanin. Different amounts of each type of melanin produce different hair colors:
|Hair Color||Type and Amount of Melanin|
|Black||Large amount of eumelanin|
|Brown||Moderate amount of eumelanin|
|Blond||Very little eumelanin|
|Red||Mostly pheomelanin with a little eumelanin|
Scientists have made limited discoveries about the many genes that predict hair color. One particular gene, known as MC1R, appears in different variations and is sometimes deactivated. When the gene is deactivated, it lowers the amount of melanin and increases the amount of pheomelanin. More pheomelanin is associated with lighter hair colors such as strawberry blond. We know this happens rarely, as approximately 90% of the world’s population has brown or black hair. 5
Regarding hair structure, genetics play a role in whether or not a person has straight, wavy or curly hair. Many different genes affect hair structure and texture, and tend to express similarly in people of the same geographic backgrounds.
Other factors also affect hair and may change it from its original state. Hormones, medications and hair styling chemicals may change the appearance of someone’s hair, as well as texture and thickness changes that come with age. 6
Skin and Complexion
The tone of a baby’s skin is determined in the same way that eye and hair color are determined. Various gene mutations produce different amounts of pigment, resulting in skin color on a continuum from pale white to black. Most people of European descent have a gene variation that produces less pigment, which explains the lighter-colored skin.
Unlike eye, hair and skin color, a person’s weight is determined not only by genetic features but also by lifestyle. Regardless of the genetics that may predispose someone to be a normal weight or overweight, food choice, exercise and sleep habits all have significant effect. The egg recipient’s in-utero and post-partum lifestyle affects the weight of her child.
The majority of height is determined by genetic inheritance. Humans’ full-grown heights are an example of polygenic inheritance, which means that height is determined by many different gene variants. This explains why most people grow to be about as tall as their parents, but it is very possible for siblings to have drastically different heights. Beyond genetics, height may also be affected by environmental elements like nutrition, hormones, and even socioeconomic status and education level. 7
Blood Type and Rh Factor
Determining a baby’s blood type is more complicated than just combining the blood types of the parents. There are 6 blood genotypes, but they do not all produce the same proteins, so the result is 4 different blood types: O, A, B, AB. In addition, when the protein known as Rh Factor is present in the blood, the blood type is positive; when Rh is absent, the blood type is negative. 8
How Does Genetic Inheritance Affect Other Traits of the Baby?
In other words: who will the baby act like?
Where does intelligence come from? What about athletic prowess or musical giftedness? Genetics are responsible for a portion of these traits, but the baby’s environment has an enormous amount of control over how the traits are expressed and utilized. This means that babies are born with a genetic predisposition to a certain level of intelligence, but without a supportive environment, the genes may not be expressed in the manner they could otherwise.
Egg recipients and their partners want to understand the odds that the baby will inherit particular levels of:
- IQ and academic potential
- Skills: musical talent, athleticism, entrepreneurial inclination, etc.
- Personality and temperament
The argument of nature vs. nurture is a long and enduring one. Researchers currently believe that nature and nurture are each responsible for about 50% of a trait’s expression. Environment can only influence a certain amount of a child’s intelligence, athleticism, etc., and at some point the hard wiring of genetic code caps the potential.
“Scientists are probably just as split as they have always been on the nature vs. nurture issue,” John Protzko, a developmental psychologist at the University of California, Santa Barbara, said. “Almost all will agree that it is a mix of both; but that is largely where progress ends.” 8
Choosing an Egg Donor Based on Genetic Traits
In other words: should I choose an egg donor who looks like me?
Many egg recipients want to understand if choosing a donor with similar eye color, hair color and other traits will increase the chance of familial resemblance. Some couples choose to use an egg donated from a family member, in hopes that the baby will better resemble the recipient and her partner.
The answer to this question is unclear. As we previously discussed, the genetics involved in determining eye and hair color can be matched in the search for an egg donor, but there is no guarantee the genes will express themselves the same way. A blond-haired, brown-eyed egg donor may look very little like the resulting baby, even if they share the same basic hair and eye color.
It is important to remember that resemblance involves more than just physical traits. Children learn to mimic their parents, so even if they do not closely resemble the egg-recipient mother, by picking up on her habits and mannerisms, they still appear similar.
You may also be interested in watching #IVFANSWERS episode: Phenotype matching and donor eggs – what’s the chance the baby will look like me?
Let’s Sum it All Up
The choice to use a donor egg is extremely personal and means something different to each couple. IVF with donor eggs is more common than you may realize. The US Centers for Disease Control and Prevention estimates that 12% of IVF cycles in the United States utilize donated eggs.
Whether or not the baby will look and act like the egg recipient is still being examined. The best answer, although potentially frustrating, is “maybe.” Because of the number of gene variations for each of the traits, there are too many possibilities to accurately predict the baby’s appearance. What should bring some comfort to couples considering egg donation, is that even spontaneous, natural conception carries the same uncertainty of inherited traits. When a woman carries, nourishes and delivers a child, it is undeniably her baby, regardless of how the baby is conceived or the traits he expresses.
However you need to remember that in many countries (also in popular destinations for an egg donation treatment in Europe) the phenotype matching donor-to-recipient is required according to the law.
You may be interested in watching recorded #IVFWEBINAR: 5 most common concerns about egg donation
- Witkin, Georgia. “The Truth About Egg Donation.” Psychology Today, Sussex Publishers, 20 June 2018, www.psychologytoday.com/us/blog/the-chronicles-infertility/201806/the-truth-about-egg-donation
- “Will My DNA Pass to My Baby If I Use Donor Eggs?” The Bird and the Bee, thebirdandthebee.co/home/2017/4/20/do-infertile-mothers-who-use-donor-eggs-pass-dna-to-their-child-the-facts-will-suprise-you
- “Is Eye Color Determined by Genetics? – Genetics Home Reference – NIH.” U.S. National Library of Medicine, National Institutes of Health, 23 Oct. 2018, ghr.nlm.nih.gov/primer/traits/eyecolor
- Starr, Barry. “How Blue Eyed Parents Can Have Brown Eyed Children.” Understanding Genetics, 27 July 2012, genetics.thetech.org/how-blue-eyed-parents-can-have-brown-eyed-children
- “Is Hair Color Determined by Genetics? – Genetics Home Reference – NIH.” U.S. National Library of Medicine, National Institutes of Health, 23 Oct. 2018, ghr.nlm.nih.gov/primer/traits/haircolor
- “Is Hair Texture Determined by Genetics? – Genetics Home Reference – NIH.” U.S. National Library of Medicine, National Institutes of Health, 23 Oct. 2018, ghr.nlm.nih.gov/primer/traits/hairtexture
- “Is Height Determined by Genetics? – Genetics Home Reference – NIH.” U.S. National Library of Medicine, National Institutes of Health, 23 Oct. 2018, ghr.nlm.nih.gov/primer/traits/height
- “Blood Types.” & Groups Chart | A, B, AB & O | Red Cross Blood Services, www.redcrossblood.org/donate-blood/how-to-donate/types-of-blood-donations/blood-types.html
- Gregoire, Carolyn. “Children’s ‘Intelligence’ Can Fluctuate Much More Than We Thought.” The Huffington Post, TheHuffingtonPost.com, 18 Mar. 2016, www.huffingtonpost.com/entry/nature-versus-nurture-children-intelligence-study_us_56eabd16e4b0b25c91848f54