Pregnant Dogs and Women Have One Surprising Thing in Common

Pregnancy is an astounding feat of nature — yet the most remarkable changes aren’t even visible to the human eye, but take place within the body’s cells.

During pregnancy, the body’s metabolic processes basically go into overdrive to support the demands of a fast-growing, hungry fetus. Metabolism is the cellular process that the body uses to convert nutrition in food to energy for almost all vital functions. These accelerated metabolic changes are especially apparent in pregnant dogs, who typically carry the fetus for just over two months on average.

But despite their considerably shorter pregnancies, dogs may actually share some key metabolic similarities with gestating women, according to a new study. The research could help scientists unpack poor pregnancy outcomes like pregnancy-related diabetes or malnutrition, whose relationship to metabolic changes is still not well understood. The findings were published Wednesday in the journal PLOS ONE.

“Humans and dogs have a different metabolism and different physiology in regard to pregnancy. However, some metabolites show similar patterns in humans and dogs,” Sebastian Arlt, lead author on the study from the University of Zurich’s Clinic of Reproductive Medicine, tells Inverse.

Pregnancy and Metabolic Changes

During metabolism, the body breaks down nutrients from food, fat, and muscles and produces small molecular byproducts known as metabolites. The study of these small molecules — ranging from amino acids to glucose — is an emerging field known as metabolomics.

There are two types of metabolites: primary and secondary. Primary metabolites are essential for growth and development, whereas secondary metabolites are not as crucial but could still affect bodily functions. Cells synthesize these primary metabolites, especially during pregnancy, to maintain bodily functions and fuel growth.

To maintain a healthy pregnancy and fetus, the body requires adequate nutrients — via these metabolites — to develop everything from tissues to organs. Put simply: metabolism helps keep pregnancies and fetal growth on track.

“It has been claimed that even small deviations of the metabolism from the norm during pregnancy could have serious consequences for the mother and the offspring,” researchers write in the study.

Yet, despite the significance of metabolism during pregnancy, scientists still don’t fully understand how metabolites affect pregnancy outcomes in mammals — whether they be dogs or humans.

“It can be assumed that the female body has to cope with a lot of metabolic changes. A lot of these changes are only partly understood,” Arlt says

Dog-Human Similarities in Pregnancy

In the latest PLOS ONE study, researchers analyzed how these metabolites fluctuate over the course of pregnancy and lactation in canines. They studied the blood of 27 pregnant dogs from more than 20 breeds ranging from bulldogs to golden retrievers and compared the data to prior research on metabolites in pregnant women.

Researchers detected key similarities between the levels of certain metabolites in both pregnant dogs and in pregnant women. Specifically, they found similar patterns between the following metabolites in both dogs and humans:

• Albumin
• GlycA
• Fatty acids
• Lipoproteins
• Glucose
• Some amino acids

Each of these metabolites serves a different role in the body. Albumin, for example, is a protein produced by the liver, and researchers found the metabolite significantly declines in the later stage of pregnancy in both dogs and women. Decline in albumin has been associated with eclampsia — a condition where seizures occur during pregnancy.

Similarly, fatty acids are necessary for healthy fetal development, and certain fatty acids like omega-3 can help bring down inflammation during pregnancy. Lipoproteins are particles made up of fat and protein, which transport cholesterol.

You’re probably familiar with the two categories of cholesterol: high-density lipoprotein (HDL) and tlow-density lipoprotein (LDL). Medical professionals often colloquially refer to HDL as “good” cholesterol and LDL as “bad” cholesterol.

You’ve also likely heard of another one of the metabolites: glucose. All the major nutrients our body consumes — like carbs and protein — eventually break down into glucose, which moves through our body’s bloodstream as blood sugar. Glucose provides the energy that fuels both the pregnant body and a growing fetus during pregnancy.

The PLOS ONE study is the first paper to analyze metabolic changes in pregnancy and lactation in dogs, paving the way for medical comparisons between pregnancy in canines and gestation in humans.

“Several metabolomics studies have been conducted in humans to address...metabolic changes during pregnancy, but no previous studies have been conducted in dogs,” write the researchers.

Can This Research Help Us Better Understand Human Pregnancy?

There are good reasons to be cautious about comparing pregnant dogs to humans. Despite being human’s best friend, canines hail from an entirely different evolutionary lineage, though some research suggests there is a sister relationship between primates and carnivores like dogs. There are also limitations to this study, which analyzed privately-owned dogs whose diet was outside the researchers’ control.

But there are also practical reasons to study and compare canine pregnancy to humans. Arlt says humans and dogs share similar “life conditions” such as environment, circadian rhythm and even food — well, sometimes. We’ve literally co-evolved side-by-side. For these reasons, scientists have studied cancer in dogs with hopes of better treating the disease in their human owners.

There’s another reason to specifically study pregnant dogs and women. Arlt likens canine pregnancy to a sped-up or “fast motion” pregnancy process — compared to the nine-month gestation in humans. Pregnant dogs often give birth to large litters of 10 puppies or more, leading to greater metabolic demands during gestation. This sped-up timeline could dogs a suitable model for analyzing metabolism during pregnancy in humans, too.

“Therefore, findings in dogs may — with a careful interpretation by experts in the fields of human nutrition and physiology — help to understand specific phenomena seen in humans,” Arlt explains.

Researchers hope studying diabetes in canines can help us better understand and possibly treat poor pregnancy outcomes in humans, especially those linked to metabolic disorders. One such condition is malnutrition. Another is diabetes mellitus, which is a kind of Type 2 diabetes that occurs during pregnancy and results in high blood glucose. These metabolic-related conditions can harm the mother’s health or impair fetal development.

Arlt says studying metabolism in pregnant dogs is important to help scientists gain the necessary knowledge on the role of specific nutrients in fetal development or early diagnosis of malnutrition. So, it’s possible dogs may not only be our best friend in spirit, but they could also help scientists keep our bodies healthy as we grow new humans.

“We hope that our study contributes to this knowledge,” Arlt says.