The developing baby faces a dilemma if the supply of nutrients from the mother through the placenta is limited or unbalanced during pregnancy. The question that arises in this case is whether resources be allocated to brain growth, or to fat deposition for use as an energy reserve during the early months after birth.
Scientists at the University of Southampton have shown that the decision made could have an effect on how fat we are as children.
In a new research, scientists at the Medical Research Council (MRC) Lifecourse Epidemiology Unit at the University, performed ultrasound scans on 381 pregnant women taking part in the Southampton Women's Survey.
They measured the blood flow from the placenta to the unborn baby, and the distribution of this blood to either the liver of the baby or bypassing the liver to supply the brain and heart. This was then compared with the infant's body fatness at birth and at four years old.
The findings show that greater blood flow to the baby's liver in late pregnancy was associated with greater body fatness in the infant at birth and at age four. In contrast, lower liver blood flow and a "brain-sparing" blood flow pattern (when the blood bypasses the liver and goes to the brain) occurred when the placenta was smaller and less able to meet baby's demand for essential nutrients in the womb.
These findings were independent of an association between mother's body fatness and the body fatness of her infant.
"In our evolutionary past, the demands of a big brain have led the unborn baby to develop blood flow responses which preserve nutrient delivery to the brain when the supply of essential nutrients from the mother cannot meet the baby's requirements," explained Keith Godfrey, Professor of Epidemiology and Human Development, at the University who led the study.
"However, having a big brain has also led to evolution of a strategy to adjust blood flow through the baby's liver, which enables the liver to produce more fat - this acts as an energy reserve, protecting brain development during periods of illness or under-nutrition in early infancy. Our data suggests that evolution of this strategy has brought with it a predisposition to obesity and later diabetes in contemporary societies with abundant nutrition in later postnatal life," he said.
Professors Guttorm Haugen from the University of Oslo and Torvid Kiserud from the University of Bergen were part of the research team.
They commented: "An interpretation of our findings is that there could be programmed effects on the liver that arise from blood flow adaptations in the womb and predispose individuals to gain excess body fat. Although further studies are needed, our findings add weight to current concerns that the current epidemic of childhood obesity and associated disorders may partly have its origins through adaptations made by the developing baby during pregnancy."
The research has been just published in the journal PLoS ONE.