Dad’s genes make a baby ‘greedy’ in the womb

Every womb is a battlefield.

There’s a tug of war happening whenever a fetus is developing, as the baby needs nutrients from the mother to grow.

But the mother needs enough nutrients in her system for her own health and to safely deliver the baby and then breastfeed her newborn.

The conflict between those two competing sides — mother versus baby — is driven by genes inherited from each parent, according to new research published in Cell Metabolism.

Genes inherited from the father will pull nutrients to the developing fetus — specifically, its IGF2 gene, which helps make a protein called “insulin-like growth factor 2.”

Thanks to dad and his hungry little IGF2, healthy fetal growth occurs and important fetal tissues like the placenta, liver and brain can get the nutrients that they need to develop.

“Genes controlled by the father are ‘greedy’ and ‘selfish’ and will tend to manipulate maternal resources for the benefit of the fetuses, so to grow them big and fittest,” Dr. Miguel Constancia, study co-author based at the Wellcome-MRC Institute of Metabolic Science in the UK, said in a news release.

But the mother’s genes are selfish, too, and they’re not giving up without a fight. Her genes will try to limit fetal growth and keep enough glucose and fats circulating in her system for her well-being.

“Those genes from the mother that limit fetal growth are thought to be a mother’s way of ensuring her survival, so she doesn’t have a baby that takes all the nutrients and is too big and challenging to birth,” said Amanda Sferruzzi-Perri, professor at the University of Cambridge and co-author of the paper.

“Although pregnancy is largely cooperative, there is a big arena for potential conflict between the mother and the baby, with imprinted genes and the placenta thought to play key roles,” said Constancia.

Researchers made their discovery by deleting the expression of IGF2 in pregnant mice. That impacted the way the mother’s pancreas produces insulin, and how her liver and other organs respond.

“If the function of IGF2 from the father is switched off … the mother doesn’t make enough amounts of glucose and lipids — fats — available in her circulation,” said Dr. Jorge Lopez-Tello, lead author of the study.

“These nutrients therefore reach the fetus in insufficient amounts and the fetus doesn’t grow properly,” Lopez-Tello added. When that happened with mice, their babies were smaller at birth and showed signs of diabetes and obesity later in life.

The research underscores the complex and critical role played by the placenta during pregnancy.

“The placenta is an amazing organ,” Sferruzzi-Perri said. “[T]he memories of how the placenta was functioning leaves a lasting legacy on the way those fetal organs have developed and then how they’re going to function through life.”