Frequent placental contractions at the heart of normal pregnancies

By Elodie Vaz | Published on May 12, 2026 | 4 min read


The placenta is a temporary yet essential organ for the proper progression of pregnancy. Acting as the interface between mother and fetus, it ensures the gaseous, nutritional, and hormonal exchanges necessary for embryonic development. Despite its central role, however, clinical monitoring of the placenta remains indirect, relying mainly on the assessment of fetal growth and certain physiological parameters. This lack of direct observation limits a detailed understanding of its functioning, even though placental dysfunction remains a major cause of obstetric complications and stillbirths.  

Previous studies had already suggested the existence of localized placental contractions distinct from traditional uterine contractions. However, their fundamental characteristics and frequency remained poorly defined.

Characterizing placental contractions

In a study published on April 29, 2026, in PLOS One, a team from the University of Nottingham sought to better understand these phenomena. The objective was to precisely characterize placental contractions and determine their frequency in physiological pregnancies, while distinguishing them from contractions of the uterine wall.  

As Dr. Louise Dewick emphasized, “This research is essential for better understanding the precise functioning of the placenta during pregnancy.”

MRI and artificial intelligence serving observation

The researchers recruited 36 healthy pregnant women between 29 and 42 weeks of gestation. Each participant underwent magnetic resonance imaging (MRI) for a duration ranging from 15 to 32 minutes.

Data analysis relied on an automated neural network capable of tracking, in real time, variations in the volume, surface area, and morphology of both the placenta and uterus. This approach made it possible to objectively assess contractile dynamics with unprecedented precision.

Contractions observed in 60% of cases

The results revealed that placental contractions occur in at least 60% of the healthy pregnancies studied. Their median frequency was approximately two episodes per hour, with an average duration of 2.4 minutes.  

Unlike uterine contractions, placental contractions produced greater changes in placental shape and lasted longer. All contractions observed—whether placental or uterine—were associated with an increase in an MRI signal linked to the presence of deoxygenated blood. A key element of the study was the identification of a morphological marker: the degree of placental sphericity. The researchers demonstrated that this variation in shape could help automatically distinguish placental contractions from uterine contractions.  

Dr. Dewick explained: “Using magnetic resonance imaging (MRI), we were able, for the first time, to clearly characterize placental contractions. We showed that they occurred in at least 60% of healthy pregnant participants, with an average frequency of two contractions per hour lasting 2.4 minutes.”

New tools for placental monitoring

Despite certain limitations—notably the relatively small sample size and the short duration of imaging sessions—this study provides fundamental insights into placental physiology. It opens the way toward a better understanding of the contractile mechanisms of this organ. According to Professor Penny Gowland, “Advances in MRI allow us to use imaging to precisely determine what is happening inside a pregnant woman’s body […] they could also help improve the screening of potential problems during pregnancy.”  

These findings therefore lay the groundwork for future studies comparing these contractions in pathological conditions such as intrauterine growth restriction or preeclampsia. Ultimately, identifying functional placental signatures could transform screening and monitoring strategies for high-risk pregnancies.  

Finally, as Amy Turnball highlighted, this breakthrough was made possible through close interdisciplinary collaboration: “What struck me most about this project was working within an interdisciplinary team […] to make a completely unprecedented discovery.” Such a collaborative approach may prove crucial in uncovering the still largely unknown mechanisms of this vital organ.    



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About the Author – Elodie Vaz
Health journalist, CFPJ graduate (2023).
Élodie explores the marks diseases leave on bodies and, more broadly, on human life. A registered nurse since 2010, she spent twelve years at patients’ bedsides before exchanging her stethoscope for a notebook. She now investigates the links between environment and health, convinced that the vitality of life cannot be reduced to that of humans