Scientists Tracked How Pregnancy Rewires Every Organ In The Body

When it’s time to bring new life into the world, the human body transforms itself in remarkable ways. The immune system, which usually fights off anything that reads as foreign, learns to chill out so it doesn’t attack the baby; the uterus stretches and expands; the cardiovascular system grows stronger so it can pump more blood; and the kidneys and liver bulk up to process waste for two.

Yet, with all these amazing adaptations part and parcel of pregnancy, there’s still a lot of mystery surrounding the orchestra of changes happening. One group of researchers in China has created a metabolic treasure map that aims to demystify our understanding of this intricate process.

Comparing tissue samples collected from nonpregnant and pregnant crab-eating macaques, the researchers discovered that pregnancy rewires metabolic processes in contrasting yet dynamic ways throughout pregnancy across 23 different tissues from organs such as the heart, kidneys, and even skin. They identified 91 different metabolites — or chemicals produced by metabolism — involved in these changes; two standout stars were the steroid hormone corticosterone and a building block of fat called palmitoyl-carnitine.

The researchers say their findings, published last week in the journal Cell, illuminate the body’s tremendous metamorphosis during pregnancy. Moreover, their study may hold the key to improving maternal and fetal health by focusing a spotlight on these metabolic changes underpinning pregnancy-related diseases like preeclampsia and gestational diabetes.

Metabolic pregnancy atlas

While scientists do have some idea of the metabolic changes the body undergoes to provide for the developing fetus, large gaps in knowledge remain because it’s simply impossible to investigate that without being deeply invasive, such as collecting tissue samples from various organs, such as the uterus, and even the placenta.

However, research in rodents has somewhat peeled back the curtain on these complex processes. They've shown that genes related to metabolism in the mother's organs and the placenta go through well-orchestrated adjustments to support the pregnancy, tweaking how the body handles its and the baby’s new energy and nutritional demands.

Analysis of human maternal blood samples has started to map out the intricate flux of metabolites over the course of pregnancy, some of which could be used like biological milestones to help predict crucial moments like how far along the pregnancy is, when the baby might arrive, and even the risk of preeclampsia, a serious pregnancy complication characterized by high blood pressure that can be life-threatening if left untreated.

But rodents aren’t the best models for a normal human pregnancy, so for their study, the researchers of the new paper turned to the crab-eating macaque, an invaluable non-human primate model used extensively in biomedical research that shares many similarities to humans in terms of how their bodies work (especially reproduction) and even how their metabolisms function.

The researchers obtained tissue samples from pregnant monkeys at three different time points: early, mid, and late pregnancy (crab-eating macaques have a gestational period of roughly 165 days). These samples were compared to their nonpregnant counterparts. The team collected samples from 23 different tissues across 10 organ systems, which included the uterus, ovaries, placenta, mammary glands, thymus (a small organ under the breastbone involved in the immune system), heart, pancreas, liver, kidneys, adrenal glands, spinal cord, skin, leg muscles, and blood serum.

They found 91 metabolites common to all the tissues across the different stages of pregnancy, although these varied in quantity. Some of these metabolites involved steroids, like progesterone, which were being produced and exerting their influence in unexpected places like the adrenal glands, pancreas, heart, and even the skin. This surprising finding suggests the production of steroids plays a broader role in adapting a person’s body for the challenges of pregnancy, potentially aiding in the growth of organs like the pancreas and heart, though further research is needed to fully understand these connections.

Another crucial finding the researchers uncovered was that corticosterone increases in many organ systems during pregnancy, which was a bit of a surprise because it's usually not considered as important as the stress hormone cortisol. However, this research shows that corticosterone is key to helping the placenta grow and develop, overall keeping a pregnancy running smoothly.

There may also be a link with preeclampsia, a metabolic disorder affecting five to seven percent of pregnancies. Pregnant crab-eating macaques demonstrated higher levels of corticosterone, which contrasted with a separate study the researchers did that found the steroid hormone was lower in pregnant people with preeclampsia. This could mean that testing for targeting corticosterone might be used in the future to mitigate preeclampsia.

These findings are far from final and do have some limitations, namely being a non-human-based study. However, the researchers hope their efforts will “serve as a resource for future research into female metabolism,” paving the way to optimizing maternal and fetal health.