Pregnancy is a genetic battleground – how conflicts of interest pit mum and dad’s genes against each other

Jessica D. Ayers, Boise State University

Baby showers. Babymoons. Baby arrival parties. There are plenty of opportunities to celebrate the 40-week transition into parenthood. Often, these celebrations implicitly assume that pregnancy is cooperative and mutually beneficial for both parent and fetus. But this belief obscures a more interesting truth about pregnancy: mother and fetus may not coexist peacefully in the same body at all.

At the most fundamental level, there is a conflict between the interests of the parent and the fetus. Although it may seem like the start of a thriller, this genetic conflict is an integral part of pregnancy, resulting in typical growth and development both during pregnancy and throughout an individual’s life – this on what my research focuses on.

However, even though genetic conflict is normal during pregnancy, it can play a role in pregnancy complications and developmental disabilities when left unchecked.

What is a genetic conflict?

Pregnancy is generally considered as a period in which a new individual is created from a unified mixture of genes from its parents. But that’s not entirely accurate.

The genes a fetus receives from each parent carry slightly different instructions for development. This means that there are contrasting and sometimes conflicting plans for how to build the new individual. The conflict over the plan for the growth and development of the fetus is the essence of the genetic conflict that arises during pregnancy.

Moms have to use their bodies to help the fetus grow during pregnancy while dads don’t. This means that the genes that the fetus inherits from the mother must not only provide for the needs of the current fetus, but also try to keep the mother alive and healthy and ensure that there are resources left for a potential future pregnancy. . These reserves include both biological resources such as glucose, protein, iron and calcium, as well as the time and energy needed to support her children after birth as they grow and develop.

Dad’s genes don’t have that same pressure because they don’t use their bodies to help the fetus grow during pregnancy. So a father’s genes don’t need to ensure that anyone other than the current fetus thrives.

To better understand this situation, imagine that all the resources a mother can give her children come in the form of a milkshake. Once the milkshake runs out, mom has nothing left to give her children. Maternal genes therefore want each child to drink only the amount they need to grow and develop. This ensures that the milkshake can be “shared” among all current and future children.

Paternal genes, on the other hand, have no such guarantee of representation in that mother’s other children – the father of the current child may not be the father of the mother’s potential future children. This lack of guaranteed genetic representation means there is no pressure on the father to “share” the milkshake. So the best strategy when it comes to paternal genes is for the fetus to drink as much milkshake as possible.

These two strategies play a figurative game of tug of war throughout pregnancy. Both sides try to pull the developing fetus a bit more towards their side. Paternal genes encourage the fetus to grow and develop rapidly and consume more resources, while maternal genes encourage the fetus to grow and use only what is necessary for its proper development. Conflicts over how deep the embryo is implanted in the uterus and how quickly the placenta and fetus develop are just a few areas where researchers have documented this tussle during pregnancy.

The milkshake problem helps researchers determine where to look for genetic conflict by simplifying where trade-offs may take place during pregnancy. Because fetal growth is central to genetic conflict, researchers have focused on processes where conflicts over resource transfers from mother to fetus can be observed. These investigations showed that the placenta, a fetal organ responsible for all resource transfers during pregnancy, is dominated by paternally expressed genes. It releases insulin-like growth factors of paternal origin that make the mother less sensitive to her own insulin and hormones that increase maternal blood pressure, ultimately increasing the amount of resources the fetus can use to grow during pregnancy, but may harm. mother’s health.

Genetic conflict and pregnancy complications

If the genetic conflict is not controlled, it can lead to pregnancy complications for the mother and developmental problems for the child. In fact, there is a growing consensus among researchers that some of the most well-known pregnancy complications like preeclampsia, gestational diabetes, miscarriages, and premature birth can best be explained by uncontrolled genetic conflict.

Despite the potential role that genetic conflict plays in pregnancy complications, current medical treatments are reactive rather than proactive. A pregnant person must show signs of complications before medical interventions and treatments can take place.

Knowing how uncontrolled genetic conflict contributes to pregnancy complications could provide researchers with another avenue to develop proactive and, ideally, preventative treatments. However, there is currently no treatment for pregnancy complications that takes into account genetic conflicts. Although gestational diabetes can be attributed to an underlying genetic conflict, a pregnant person must have high blood sugar levels before doctors can treat the underlying conflict regarding insulin production and blood sugar levels.

The experiences of pregnant women during the COVID-19 pandemic provide an example of why more research into genetic conflict is needed. During the pandemic, doctors have seen both a dramatic decrease in the number of premature births as well as an increase in the number of stillbirths and miscarriages. Both types of complications are influenced by genetic conflict, but the reasons for these opposing trends are unclear.

As a pregnant woman at the start of the pandemic, my pregnancy was scary and stressful, spent at home away from the pressures of “normal” life. Further research into the complex process of pregnancy and the role of genetic conflict in complications could help researchers better understand how the changes brought about by the pandemic produced such different pregnancy outcomes.

Jessica D. Ayers, Assistant Professor of Psychological Sciences, Boise State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.