Obesity Induced by a High-Fat Diet May Impair Placental Function

Guest written by KaLynn Harlow, PhD Candidate in Reproductive Endocrinology

While the importance of nutrition during pregnancy is commonly stressed, specific recommendations are not always grounded in evidence. Research has recently found that obesity induced by a high-fat diet may impair the function of the placenta, thereby harming the developing offspring. Of note, the latest Dietary Guidelines for America from the USDA found that 71% of American females aged 19-30 and 70% of American females aged 31-59 are consuming more than the recommended amount of saturated fats. Western-style diets tend to contain higher levels of dietary fat, especially saturated fat, in higher-convenience foods. 

Early in pregnancy, the placenta, a new organ that serves as the lifeline between mother and infant, is created, which houses and nourishes the fetus until it is born. The placenta carries nutrients and other essentials to the fetus while also removing harmful waste. By examining it, scientists are learning important information about how embryos and fetuses develop, as well as the impacts of the mother’s lifestyle.

To learn more about how high-fat diets in the mother can impact the development of the placenta, researchers in Germany conducted an exploratory study using female mice (dams). These mice were fed a high-fat diet until they reached an obese state and then through pregnancy. When the placentas from obese mice were analyzed in the early stage of the third trimester, researchers found changes in how the cells of the placenta developed when compared to placentas from non-obese mice fed a standard chow diet. Researchers found there was an increase in the capacity for obese mothers to transfer nutrients to and harmful waste away from the growing offspring. However, after further inspection, they found that placentas from the obese mice did not perform as well for the offspring. Specifically, the placental transfer zone, or the region where the dam is physically connected to the placenta, had a poorer connection between mother and pup. Despite there being a potentially greater transfer capacity, there wasn’t as much transfer ability. Another way to think of this is like a faulty phone charger. A poor connection means it will take longer for a device to charge (or maybe even experience electrical issues). In the case of the placenta, the pup suffers if the connection to the mother is poor, too. In the experiment, obese mothers had significantly smaller fetuses than fetuses from non-obese mothers, despite the placentas being similar in weight between the two groups. Placental size is often related to fetus size, so this is further evidence that despite the placenta being capable of housing a bigger baby, the connection was a limiting factor preventing maximum growth.

While it cannot be assumed that animal studies are always directly transferable to humans, this exploratory study reveals high-fat diets may negatively impact the development of the placenta and subsequently hinder the growth of the offspring. The role of the placenta cannot be overstated during pregnancy. If these mice experienced issues in placental development that could be attributed directly to the high-fat diet or obesity of the mother, this certainly provides us with more information regarding the importance of nutrition recommendations for dietary fat during pregnancy. At this time, more research is necessary to make human-specific recommendations. 

Peer-edited by Kara McIver

Resource: Kretschmer, T., Turnwald, E. M., Janoschek, R., Zentis, P., Bae-Gartz, I., Beers, T., … & Appel, S. (2020). Maternal high fat diet-induced obesity affects trophoblast differentiation and placental function in mice. Biology of Reproduction, 103(6), 1260-1274.

Picture credit: Pixabay