Last updated on Jun 22nd, 2021 at 04:43 pm

For pregnant women over 35, placenta changes could negatively affect their male infants…

Fifty years ago, it was the norm for women to have kids in their early twenties. Today, it’s seemingly more common for women to start a family in their 30s.

The downside of starting a family later in life is that changes that occur in the placenta in older pregnant mothers may lead to a greater likelihood of poor health, particularly in their male offspring.

Women over 35 are considered to be of advanced maternal age. For the study, researchers analysed the placentas of young (three to four months old) and aged rats (nine and a half to 10 months old) that correspond to approximately 35-year-old humans.

Rats are a useful model as their biology and physiology have a number of important characteristics in common with those of humans.

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Babies are smaller

Researchers found that both male and female foetuses do not grow as large in older mothers, but there are sex-specific differences in changes to placental development and function.

Female foetuses are better supported

They found that in aged mothers, the placenta of female foetuses showed beneficial changes in structure and function that would maximise the support of foetal growth.

In some instances, the placenta even supported the female foetus better than the placenta of a younger mother.

Male foetus’s growth is limited

In the case of male foetuses, the placenta showed changes that would limit foetal growth in the aged pregnant rats.

“A pregnancy at an older age is a costly proposition for the mother, whose body has to decide how nutrients are shared with the foetus. That’s why, overall, foetuses do not grow sufficiently during pregnancy when the mother is older compared to when she is young,” says Dr Tina Napso, a postdoctoral fellow at the University of Cambridge and first author of the study.

“We now know that growth, as well as gene expression in the placenta is affected in older mothers in a manner that partially depends on sex: changes in the placentas of male foetuses are generally detrimental.”

Common pregnancy complications in older moms

Pregnancy in older mothers is associated with a heightened risk of complications for both the mother and her baby. These include preeclampsia – raised blood pressure in the mother during pregnancy, gestational diabetes, stillbirth and foetal growth restriction.

Until now there has been a limited understanding of how the placenta is altered by advanced maternal age.

“With the average age of first pregnancy in women becoming higher and higher, and especially so in developed countries, it is very important to understand how the age of the mother and the sex of the baby interact to determine pregnancy and later-life health of the child,” says Dr Amanda Sferruzzi-Perri, lead author of the study and a Royal Society Fellow in the Centre for Trophoblast Research at the University of Cambridge’s Department of Physiology, Development and Neuroscience.

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The important role of the placenta

The placenta transports nutrients and oxygen from mother to foetus, secretes signalling factors into the mother so she supports foetal development, and is the main protective barrier for the foetus against toxins, bacteria, and hormones – such as stress hormones – in the mother’s blood.

It is highly dynamic in nature, and its function can change to help protect the growing foetus when conditions become less favourable for its development, for example through a lack of nutrients or oxygen or when the mother is stressed.

Offspring of older moms have poor heart function

An earlier study performed by the collaborators showed that offspring from mothers who enter pregnancy at an older age have poor heart function and high blood pressure as young adults, and particularly so if they are male.

Although further studies in humans are required, the results suggest the importance of considering the sex of the foetus when giving advice to older pregnant women.

The researchers also hope to build on these results and find ways of improving the function of the placenta to optimise foetus growth.

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Source: University of Cambridge via

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