New research provides the first clear evidence that the amount of nutrients transported to the foetus by the placenta adjusts according to both the foetal drive for growth, and the mother’s physical ability to provide.
Researchers have shown for the first time how the placenta “umpires” a fight for nutrients between a pregnant mother and her unborn baby. The study suggests that the placenta will adjust the amount of nutrients transported to the foetus for growth in line with the mother’s physical ability to supply.
The findings, published in the journal PNAS, suggest that if the bodily environment that a mother provides for her baby is unfavourable, for example through small body size or metabolic dysfunction, the placenta will change the flow of nutrients to the foetus relative to her own state. This can affect foetal development, resulting in complications at birth.
It is the first time that scientists have been able to provide clear evidence that the placenta plays the decisive role in this delicate balancing act, rather than merely acting as a passive interface which enables the transfer of nutrients from mother to foetus.
The study, by researchers at the University of Cambridge, involved making a precise genetic change in mice, which caused poor growth and changed the mother’s bodily environment. They then observed how the placenta developed and acted in response, finding that in mothers in which this alteration had been made, the structure of the placenta was different, and fewer nutrients reached the foetus.
A better understanding of how the placenta manages the trade-off will eventually enable researchers to reduce pregnancy complications in both humans and other mammals.
The study was led by Dr Amanda Sferruzzi-Perri, a Research Associate at St John’s College, University of Cambridge, and is part of a five-year project in the Department of Physiology, Development and Neuroscience examining the relationship between the placenta and pregnancy complications.
“During pregnancy there is a kind of ‘tug-of-war’ going on between the mother and the foetus over who gets the nutrients that the mother ingests,” Sferruzzi-Perri said. “This work shows for the first time that the placenta is the umpire which controls that fight. Understanding more about the placenta’s role is extremely important. If nutrients cannot be divided correctly during pregnancy, it can lead to life-threatening complications for expectant mothers, and long-term health consequences for both mother and child.”
At least one in every eight pregnancies in the UK is affected by complications stemming from impairment of the placenta. In the developing world the rate is even higher, with at least one in every five pregnant women affected. The potential consequences include abnormal birth weight, premature delivery, pre-eclampsia, and maternal diabetes.
A major cause appears to be the placenta’s response to unfavourable biological changes in the mother herself. These may, for example, be the result of poor nutrition, high stress levels, metabolic dysfunction, or obesity.
How the placenta allocates nutrients in these situations, however, and the hormonal signals that the placenta may be releasing while doing so, is not fully understood. By understanding these processes better, researchers hope to identify both the biological early warning signals that a problem has arisen, and their relationship to specific causes, enabling them to develop therapeutic interventions that reduce the number of complications overall.
The new study represents a step towards those aims because researchers were a