The Overlooked Half of the Story: The Paternal Role in Pregnancy, Placenta, and Birth Outcomes
When we talk about fertility, pregnancy, and birth outcomes, we overwhelmingly focus on the body of the birthing parent. If something goes wrong—a miscarriage, preeclampsia, preterm labor, or low birth weight—it’s often framed as a failure of the mother’s body. But that’s only half the story. Mounting research reveals that the sperm-contributing parent plays a profound and direct role in shaping everything from placental health to labor timing to postpartum recovery. Yet, this science is rarely part of the mainstream conversation.
In this article, we’ll explore the genetic, epigenetic, immunological, and placental roles that sperm-contributing partners play in pregnancy and beyond—and why shifting our focus toward the full reproductive dyad could radically change the way we understand maternal and infant health.
🧬 The Genetics of Pregnancy Begin With Sperm
While both egg and sperm contribute half of the baby’s DNA, the sperm-derived DNA plays a disproportionate role in placental development—and therefore, in regulating the uterine environment.
The placenta is primarily made from fetal (not maternal) cells, and these fetal cells carry more paternally expressed genes than maternally expressed ones, particularly in the trophoblasts, which form the outer layer of the placenta.
Many imprinted genes—genes expressed in a parent-of-origin-specific manner—come from the sperm and control key growth and metabolic processes. Dysregulation of these genes is linked to complications such as preeclampsia, intrauterine growth restriction, and gestational diabetes.
🧪 Key finding: Preeclampsia has been associated with immunological maladaptation to paternal antigens in sperm, especially in new relationships or short intervals between meeting a new partner and conceiving.
🦠 Sperm Health and Epigenetics: It’s Not Just DNA
We now understand that sperm carries far more than just genetic material. It also delivers epigenetic information—chemical markers that influence how genes are expressed in the embryo and placenta.
Factors that affect sperm epigenetics:
Diet and micronutrient levels (e.g., folate, zinc, antioxidants)
Exposure to toxins (e.g., pesticides, plastics, smoking, alcohol, heavy metals)
Chronic stress and sleep quality
Age and weight
These factors alter DNA methylation patterns in sperm, which in turn influence embryo implantation, placental development, and even the offspring’s long-term health—including susceptibility to metabolic disorders, neurodevelopmental issues, and immune dysfunction.
🧬 One 2020 study found that poor sperm quality was associated with a higher risk of miscarriage, even when the maternal partner was healthy and under age 35.
🧫 Placenta: Paternally Programmed, Maternalized in Function
The placenta is essentially the baby’s first organ—and it’s co-created by both parents. But the paternal genome plays a lead role in programming its formation:
Paternal genes control placental invasion into the uterine lining, which directly influences nutrient delivery and maternal blood pressure.
Poor placental implantation or overgrowth (too shallow or too deep) is tied to paternal gene expression patterns, not just maternal ones.
🔍 Studies show that placentas from pregnancies fathered by the same partner tend to be more successful, while new paternal exposure may increase risk of preeclampsia—suggesting an immune tolerance that develops between partners over time.
🧠 Beyond Conception: The Ongoing Influence of the Paternal Parent
Even beyond fertilization and placental development, the paternal partner’s health and behaviors before and during pregnancy matter:
Supportive involvement during pregnancy is associated with lower maternal stress, which reduces cortisol exposure for the baby and improves labor outcomes.
Fathers who engage in co-regulating behavior postpartum (skin-to-skin, caregiving) contribute to maternal healing, hormonal balance, and newborn attachment.
Meanwhile, absent, unsupportive, or high-conflict dynamics are strongly associated with postpartum depression, stalled labor, and poor outcomes for both the birthing person and baby.
⚠️ Why We Must Shift the Blame (and the Focus)
When a pregnancy becomes complicated, the medical system often looks inward—to the uterus, the hormones, the weight of the pregnant person. Rarely do we ask: What was the health status of the sperm-contributing parent? What exposures, lifestyle, or conditions may have contributed to what we’re seeing now?
This imbalance reinforces the harmful narrative that when pregnancy goes “wrong,” it’s the birthing person’s fault—a deeply gendered, outdated view that erases half the biological story.
✊🏽 Centering the full reproductive dyad in our conversations about fertility, prenatal care, and birth outcomes is not just more accurate—it’s more just.
✅ Practical Steps for Paternal Health Before Conception
If you’re planning a pregnancy, here are research-backed ways the sperm-contributing parent can support a healthier outcome:
Eliminate tobacco, alcohol, and recreational drugs at least 3–6 months before conception
Improve diet: high in antioxidants (vitamin C, E), folate, zinc, selenium
Exercise regularly and maintain a healthy weight
Address sleep apnea or poor sleep
Manage stress and mental health
Avoid endocrine disruptors: plastics (especially BPA), pesticides, and synthetic fragrances
Limit heat exposure: avoid hot tubs, tight underwear, and laptop use on the lap
🧠 Final Thoughts
As birth workers, we are trained to hold space for complexity, nuance, and full-bodied truth. The idea that the maternal body is solely responsible for the outcomes of pregnancy is scientifically outdated and socially unjust. The sperm-contributing parent is not a passive participant—they are a full biological co-architect of the pregnancy and all that unfolds from it.
It’s time we started acting—and educating—accordingly.
References
Aghaeepour N, et al. (2017). An immune clock of human pregnancy. Science Immunology, 2(15).
Borges E Jr, et al. (2020). Male age is associated with sperm DNA methylation profiles and poor reproductive outcomes. Fertility and Sterility, 114(1).
Redman CWG, Sargent IL. (2005). Latest advances in understanding preeclampsia. Science, 308(5728).
Fleming TP, et al. (2018). Origins of lifetime health around the time of conception: Causes and consequences. The Lancet, 391(10132).
Soubry A, et al. (2014). Paternal obesity predicts methylation status of imprinted genes in newborns. BMC Medicine, 11(1).
McNamara PS, et al. (2022). Paternal contributions to pregnancy health and outcomes: Reframing the male role. Frontiers in Endocrinology.
Shah PS. (2010). Parental exposure to tobacco and adverse reproductive outcomes. American Journal of Obstetrics & Gynecology, 202(2).
