Sperm's Influence on a Pregnancy

Researchers are learning the many ways paternal contribution influences pregnancies

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We all know it takes two to make a baby, but even though males contribute half of the genetics, they’re often left out of the pregnancy picture. Instead, the focus is typically on the females who experience pregnancy first-hand, and if anything goes wrong, they’re usually the ones blamed.

Our highly patriarchal society and lack of research into women’s health have encouraged such beliefs. But now, thanks to cultural shifts along with scientific and technological advancements, researchers are learning some pretty astounding things about the role sperm play during pregnancy.

Placenta

I once dedicated an entire article to the placenta because it’s a miraculous organ that deserves attention. The placenta is roughly 10 inches (20 cm) wide and looks a bit like a blobby mushroom, yet it has many vital functions.

Forming about ten days after conception, the placenta single-handedly fulfills all our organs' tasks in the womb by providing us with nutrients, oxygen, protection, and removing waste. It also oversees the complete remodeling of almost 150 coiled blood vessels in the uterus, called spiral arteries, that provide the placenta with blood.

In addition to juggling and coordinating these jobs, the placenta is an intermediary between the pregnant person and fetus, and convinces the mother’s immune system not to attack the fetus. For all of these reasons and more, the Yale School of Medicine summarizes that:

“A healthy placenta is the single most important factor in producing a healthy baby.”

When complications arise with pregnancies, including health complications of the fetus and newborns or flaws in the placenta, most research focuses on maternal factors and the interactions between mother and child.

Considering pregnancy occurs in the female body, it makes sense that females tend to be the focus when something goes wrong, while far less attention is spent looking at the father. However, recent research shows the errors in this assumption.

Paternal Influence on Placental Health

The common consensus minimizes the father’s role in pregnancy to doing nothing more than depositing his genetic material during conception. However, their genetic contribution does anything but sit on the sidelines.

A 2013 study, published in the Proceedings of the National Academy of Sciences (PNAS), involving hybrids of horses and donkeys found that the placenta predominantly grows according to blueprints from the paternal genetics. In other words, the genetic instructions for building the placenta mostly come from the sperm.

Further research shows that paternally expressed genes dominate the placenta and that sperm — more specifically, the health of sperm — influences the placenta's health, fetal development, and the long-term health of the child after birth.

During pregnancy, paternal cells in the placenta release insulin-like growth factors that make the mother less sensitive to her own insulin and hormone levels, while increasing maternal blood pressure. As a result, the fetus receives more resources during development, but at the cost of the mother’s health.

But why would this happen? Why would the paternal genes predominantly form the placenta, and why would they incite processes that could harm the mother?

Victoria Male, a senior lecturer in reproductive immunology at Imperial College London, explained to Natasha Hinde of HuffPost UK how,

“In pregnancy, the mother’s and father’s genetic interests are not exactly aligned.”

Biologically speaking, it’s in the mother’s best genetic interest for her and her child to be healthy and survive. This way, she can continue caring for the child until they become more independent, and the mother can continue reproducing. But to do that, she can’t give all of her resources and energy to the fetus during pregnancy.

Meanwhile, Male points out that it’s in the father’s genetic interest for the baby to siphon as much energy and resources from the mother as possible, to make the fetus as strong and healthy as possible. And since the father can make more children with other females, the mother’s health isn’t as important. Or, in other words, as Male tells Hinde,

“The placenta is at the frontline of this battle of the sexes. The father’s genes will try to make the placenta as big as possible, to extract as much energy as possible from the mother. The mother’s genes will try to prevent the father’s genes doing this.”

This so-called “battle” between paternal and maternal genes lasts throughout a pregnancy.

And since paternal genes create most of the placenta, it would make sense that the sperm’s health would also influence the placenta’s health.

Sure enough, research has linked poor sperm quality to problems with the placenta that result in conditions like preeclampsia, a destructive pregnancy complication that affects between 2 and 20 percent of pregnant people.

Preeclampsia involves persistently high blood pressure and can result in damage to the linings of a pregnant person’s neural blood vessels, liver, kidneys, and lungs, leading to organ failure, convulsions, coma, and death. The only cure is giving birth.

Miscarriages

Some unfortunate facts about pregnancies are that about 30 percent of them will end in a miscarriage, and around 80 percent of miscarriages occur within the first trimester, or the first 12 weeks, often before a person knows they’re pregnant.

Most of the time, such a travesty is a mysterious, one-off event, but for about 1 to 5 percent of pregnant people, it happens multiple times.

Recurrent miscarriage is when someone experiences the loss of two or more pregnancies in a row. It’s what’s happening when someone says they “can get pregnant but not stay pregnant.” And since the mother experiences the pregnancy, it’s been traditionally believed that the underlying cause of miscarriages resides with them.

However, a growing pile of research is unraveling this assumption.

Now, it appears that only about half of recurrent miscarriages are the result of maternal factors, such as hormonal imbalances or an inability of the womb to support a pregnancy.

Meanwhile, a study by researchers from Imperial College London, published in the journal Clinical Chemistry, discovered a link between sperm DNA fragmentation and recurrent miscarriages.

(I found a reliable article about the study, but the US government has censored the study itself and removed it from the internet along with several other sources I found and subsequently lost while writing this article.)

DNA fragmentation refers to single- or double-stranded breaks in the sperm genome. As Adam Watkins, an Assistant Professor at the University of Nottingham, explains in The Conversation,

“As sperm cannot repair their damaged DNA, high levels of sperm DNA fragmentation is viewed as a leading cause of infertility in men.”

Similarly, research has shown that sperm quality is directly linked to a male’s health. Other studies, that I could find, show that factors like age, consuming alcohol, obesity, smoking, poor diet, pollution, infections, oxidative stress, and even underwear preference can all cause sperm DNA fragmentation.

Obesity is a particular issue when it comes to male fertility. In many countries worldwide, the rate of obesity is rising, while male fertility is declining. Studies focused on men and mice have found that sperm from overweight males are slower and are less likely to fertilize an egg or result in a healthy birth.

Age is another major factor in sperm health, as research shows that the sperm of males aged 40 or older have an increased risk of a pregnancy ending in a miscarriage, and are linked to rare birth defects, genetic problems, and cognitive challenges in the child such as autism, schizophrenia, bi-polar disorder, and childhood leukemia. Poor sperm health can also negatively impact the health of the pregnant person.

Additionally, smoking is particularly bad for sperm quality, and in fact, some research indicates that when males smoke just before conception, it increases the chances of a miscarriage. Male explained to Hinde:

“That could be an effect on the placenta, but it’s more likely to be because it increases the chance that there is a genetic problem with the whole pregnancy (both the baby and placenta).”

I know, that’s a lot to take in, and it’s unnerving to say the least. After all, with so many issues affecting sperm quality, what can males do to protect their own, their future children’s, and their children’s mothers’ health?

What Can Males Do?

Thankfully, not all is lost. There’s plenty of evidence showing that by making some lifestyle changes, prospective fathers can boost their sperm health and increase the odds of a successful pregnancy, while also decreasing the chances of a miscarriage. Male explained to Hinde that,

“We do know that drinking too much alcohol, smoking and being overweight reduce sperm count and quality. So making these lifestyle changes can help product healthier sperm, making it more likely to meet the egg in the first place.”

Ultimately, the best way for a male to take care of their sperm health is by taking care of their own overall health, especially before trying to conceive.

Perspective Shift

When pregnancies go wrong, or a female seems unable to experience a successful pregnancy, the blame is often laid at her feet, which is especially scary for any female, but especially black women, who experience a miscarriage in the United States these days, as miscarriages are increasingly being viewed as crimes comparable to murder.

Now, as science shows again and again, it’s high time we stop blaming mothers for everything and anything that goes wrong during a pregnancy. The father’s role in a pregnancy goes far beyond the act of conception. A father’s sperm practically constructs the placenta, which determines the health of an embryo and fetus in the womb, and the child’s health long after birth.

This is why science is essential. While teaching us new things, science also shows us when we’re wrong. Plus, now that we know the extent to which sperm influence pregnancies, males can be more proactive about their health to boost their chances of a successful one.

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Photo by Deon Black on Unsplash