When you have a new baby, people can’t help but comment on who he or she favors. He has his mother’s nose! His father’s eyes! It’s beautiful to see a reflection of both Mom and Dad in their new little creation, especially when those traits are mirrored strongly.
Most people know that our genes work in pairs; babies inherit one set from their mother and another from their father. Our genes determine a plethora of things—our height, eye color, risks for certain diseases, and more. They even influence our natural abilities and personalities.
What might seem less obvious, however, is how our genetics can affect the creation of the organ that temporarily connects a mother and baby: the placenta. Even though the placenta contains DNA from both his mother and father, the DNA that most impacts the embryo’s side of it is actually from his or her father. In fact, Dad’s health—and how it impacts his genes’ role in building the placenta—has some pretty important downstream effects on the health of his offspring, which we’ll discuss in this article.
How Dad’s genes build the placenta
A 2013 study from Cornell University involving horses, donkeys, and mules researched the link between a father’s genetics and the placenta. While the study didn’t involve humans, it still gave crucial insights into how placentas develop and function in all eutherians (i.e., mammals that have placentas)—which includes humans.
Keep in mind that the placenta is a flat, oval-shaped organ that nourishes the growing baby with oxygen and nutrients from the mother. When baby is in the blastocyst stage (very, very early on in development), he or she begins to produce the placenta, which contains DNA from both Mom and Dad. And while baby’s own genetic material drives the placenta’s development, Mom’s own hormones keep her uterine lining thick to maintain the pregnancy until the placenta begins producing estrogen and progesterone by the end of the first trimester. The placenta is anchored to the mother’s uterus on one side (known as the maternal side) and attached to the baby via the umbilical cord on the other side (the baby’s side). If you’ve had the privilege of seeing a childbirth in-person, you’ll know that the placenta looks very much like a ‘tree of life’ with all the blood vessels it contains. A temporary organ, the placenta will be approximately the size of a dinner plate by the time of birth, and (in the event of a vaginal birth) will be expelled by the mother’s body shortly after the baby is birthed.
Furthermore—and the placenta fact most pertinent to the topic of this article—the aforementioned 2013 Cornell study made the fascinating discovery that the paternal (i.e., Dad’s) copy of genes are favored in the placenta.
Inside the placenta, mom and dad’s genes push and pull to affect fetal growth
Not only do the genes from Dad build the placenta, but they also affect how the placenta communicates hormonally with both the mother and the baby. A 2022 study from Cambridge University discovered that one of the genes that fathers contribute to the placenta is called Igf2. Igf2 is known as a “greedy gene,” in that it communicates to the mother’s body to give more nutrients to the fetus during pregnancy. “Although pregnancy is largely cooperative, there is a big arena for potential conflict between the mother and the baby, with imprinted genes and the placenta thought to play key roles,” said researcher and study co-author, Miguel Constancia.
To wit, as the Igf2 paternal gene dials up the amount of nutrients flowing to the fetus via the placenta, another gene from the maternal side pumps the brakes. The maternal version of the gene, called Igf2r (the “r” standing for receptor), ensures that not too much nutrition goes to the baby (which would make him too large to carry and birth). Ideally, this genetic interplay creates a “Goldilocks” situation, in which the father’s genes ensure that a baby is big enough to survive, but the mother’s genes ensure that the baby is small enough to be safely born.
Understanding intrauterine growth restriction and Russell-Silver Syndrome
A better understanding of this interplay could lead to more knowledge about those situations in which something goes wrong with these genes. For example, fetuses can become growth restricted if there are genetic mutations where the Igf2 paternal gene is not present. This is an explanation for a rare genetic disorder called Russell-Silver syndrome, which begins with intrauterine growth restriction (IUGR) in pregnancy, and continues with lifelong physical effects from the lack of proper growth in the womb.
Other ways in which a father’s health impacts the health outcomes of his child
While a father cannot per se control his genes, the emerging science of epigenetics indicates that a father’s physical health also plays a crucial role in determining the health outcomes of his child.
Dad’s gut and baby’s health
For example, some research suggests that Dad’s gut microbiome may determine the proper growth of his child and the health of Mom’s pregnancy, via downstream effects on the placenta. Children born to fathers with poor gut health can have health issues of their own due to a less-than-optimal placenta in utero.
Metabolic syndrome and preterm birth
Furthermore, in a 2021 study, researchers found that children born to fathers who had metabolic syndrome (which is associated with conditions like diabetes and heart disease) had a 19% higher chance of being born preterm, 23% higher odds of low birth weight, and 28% higher chance of needing to stay in the NICU after birth.
Good news about getting healthy before conceiving
The aforementioned research connecting dad\s preconception health with infant health outcomes coincides with the research cited by Real Food for Fertility authors Lily Nichols and Lisa Hendrickson-Jack, who assert that poor sperm quality can be fixed with healthier diet and lifestyle choices, improving both chances of conception and pregnancy outcomes after conceiving. It’s also in keeping with other research finding that paternal health impacts placental development; specifically, how dad’s semen may impact mom’s preeclampsia risk.
The same diet and lifestyle modifications that are recommended for improving the health of future moms are also generally applicable to future dads. Reducing alcohol intake, quitting smoking, engaging in moderate-intensity exercise for at least 30 min 5x/week, and upping fruit and vegetable intake to a minimum of five servings per day are good, basic places to start.
The bottom line: Dad’s preconception health is as important as Mom’s is for Baby’s health
Recent research on how a father’s genetics impact pregnancy and the growth of his child has shed light on potential explanations for certain birth defects or growth restrictions, and underlined the important role a father’s preconception health and genetics play in the health of his future children. Clearly, both Mom and Dad are key in helping their children be as healthy as they can be before (and after) birth!
This information should empower hopeful parents-to-be to take their own health seriously, as it’s crucial for setting up the foundations of their childrens’ lives. In the years to come, additional research on the placenta may further underline the important role a father’s health and genetics play in building a healthy placenta, impacting his children’s health well before he ever meets them.
This article was updated on February 22, 2025, to reflect that the placenta is created by the newly conceived human, not by the mother, and contains both maternal and paternal DNA.
