Faster Placental Development Raises Preeclampsia Risk

Research revealed how heredity influences placental growth and discovered a link to an increased risk of sickness in the mother.

The placenta is an organ that develops in the womb alongside the foetus via the umbilical cord. It is the only organ that contains both mother and child tissue. The placenta delivers oxygen and nourishment to the developing foetus while also removing waste. A dysfunctional placenta is linked to pregnancy problems and an increased risk of disease in the kid.

Despite its critical significance, little is known about how the placenta regulates its growth.

"Understanding placental growth is important, as babies with very small or large placentas are at higher risk of complications", Professor Pal Rasmus Njolstad at the University of Bergen, explained.

He and his colleagues at the University of Bergen, together with colleagues in the UK and Denmark have led a large-scale international collaboration to examine placental growth in the greatest detail yet.

Together they carried out the first ever genome-wide association study of the weight of the placenta at birth, generating several revelations.

"Among the findings published in Nature Genetics, we concluded that faster growth of the placenta can contribute to the risk of preeclampsia, and to earlier delivery of the baby", said Njolstad.

The placenta is an important organ during pregnancy, providing an intricate and vital link between mother and baby.

"In our study, we have identified 40 variations in the genetic code linked to how big a placenta can grow, which improves our understanding of this vital organ in humans. Several of these genetic variations also influence the weight of the baby, but many are predominantly concerned with placental growth", Njolstad explained.

The team found that where the genetic code of the foetus meant it was more likely that the placenta would grow bigger, there was a higher risk of pre-eclampsia in the mother.

"This could be because the placenta grows too fast, which can upset the balance between the baby's demand for resources and how much the mother is able to provide, which can be a factor in pre-eclampsia that occurs late in pregnancy", said Njolstad.

Placenta growth is linked to pregnancy length. Pre-eclampsia is a condition that may develop in pregnancy, which causes high blood pressure. Some of the mother's organs, such as the kidneys and liver, stop working properly.

Detecting it early is essential to avoid severe health problems for mother and baby, yet how preeclampsia develops isn't fully understood.

"Our study suggests that faster growth of the placenta contributes to a higher risk of preeclampsia in the mother. It seems specific to placenta growth because we did not find the same risk when we looked at the genetics of baby weight", said Professor Rachel Freathy at the University of Exeter Medical School, and a co-lead of the paper.

Faster-growing placenta was also linked to shorter pregnancy.

"We found that babies with genetic code for a bigger placenta were more likely to be born earlier, which underscores the importance of investigating placental biology in studies of pregnancy duration and the timing of delivery", said another of the co-leaders of the study, senior researcher and group leader, Bjarke Feenstra at the Copenhagen University Hospital and Statens Serum Institut, Denmark.

Insulin was related to placenta growth.

One key finding from the study related to insulin, a hormone that regulates blood sugar. The foetus produces insulin in response to glucose (sugar) from the mother, which acts as a growth factor.

The team found this insulin is also linked to the growth of the placenta, which helps to explain why placentas tend to be large in pregnancies where the mother has high blood glucose due to diabetes.