Late pregnancies affect boys’ heart and blood health

Pregnancies beyond the age of 35 are considered late for the scientific world. In the United States, Canada, the United Kingdom and Australia, pregnancies in women over 35 represent between 14 and 22% of total births each year. A study published at the end of November in the journal Scientific Reports indicates that the maternal age would have consequences on the health of the fetus. According to the results of researchers from the University of Cambridge (United Kingdom), the University of Alberta (Canada) and the Robinson Research Institute of the University of Adelaide (Australia), the age of the mother would affect the efficiency of the placenta to transport nutrients to the fetus, which would lead to the development of heart and blood pressure problems in boys, reducing the growth of the latter.

Male fetuses are less pampered than others

For their study, the researchers conducted tests on rats aged 3 to 4 months (young) and 9.5 months to 10 months (old), which corresponds to humans around 35 years old. The team found that the structure and functions of the placenta are reduced in older mothers, which affects the fetuses. However, these changes are greater in male fetuses, reducing the mother’s ability to support the growth of her offspring.

In elderly mothers, changes in the structure and function of the placenta are beneficial if it is a female fetus, even going so far as to optimize the growth of the future infant. In some cases, the results were even better than those of a young mother. Conversely, for the male fetus, growth is less sustained by elderly mothers, as is their placenta, which does not function properly.

In aged rats, the glucose concentration was 11% higher than in young rats. On the other hand, the levels of insulin, leptin, cholesterol and fatty acids remain the same. On the other hand, more than half of the fetuses of old rats (55%) have a lower weight than that of young rats. This weight reduction is accompanied by a significant decrease in heart, brain and liver weights in male fetuses, but does not affect female fetuses. Finally, the efficiency of the placenta of old rats compared to young rats was reduced by 22% when the fetus was female, and by 37% when the fetus was male. Thus, at a certain stage, maternal age compromises fetal development and the effectiveness of the placenta.

Better management of late pregnancies

“Pregnancy at a later age is an expensive proposition for the mother, whose body must decide how nutrients are shared with the fetus,” says Tina Napso, a post-doctoral fellow at the University of Cambridge and first author of this study. This is why, on the whole, fetuses do not grow as much during pregnancy when the mother is older than when she is young. We now know that growth, as well as gene expression in the placenta, is affected in older mothers in ways that are partly gender-dependent: changes in the placenta of male fetuses are usually harmful.”

The study conducted on rats shows that placental changes in elderly females may be linked to a greater likelihood of poor health in their male offspring. Although the growth of both male and female fetuses were found to be reduced in older mothers, the study also revealed sex-specific differences in fetal changes and development, which increases the risk that the Older woman’s children show heart and blood pressure problems in old age, especially in men.

“This new understanding of placental development and function could contribute to better management of human pregnancies and the development of targeted interventions to improve the long-term health of children born to older mothers,” suggests Tina Napso.

The study results also indicate that pregnancy at a later age also increases the risk of complications such as pre-eclampsia, gestational diabetes, increased risk of stillbirth and fetal growth restrictions. So far, studies conducted have not been able to give a full understanding of how the placenta changes with the age of the mother.

A 2015 study already came to the same conclusion.

This research built on an earlier study dated 2015 and published in the journal Hypertension, which linked maternal age to later heart and blood pressure complications in children, especially boys. This new study helps to better understand how it works and explains why the fetus is not supported in the same way by the uterus of the elderly mother depending on its sex.

Dr Amanda Sferruzzi-Perri, lead author of the study and a fellow in the Department of Physiology, Development and Neurosciences at the University of Cambridge, says the study is also gaining in importance as the average age of first pregnancy among women, especially in developed countries, is increasingly high. A better understanding of placental changes could help manage pregnancy and ensure optimal fetal growth.

The researchers recommend that more studies be carried out in humans and insist on the need to take into account the sex of the fetus in pregnant women over 35 years of age.