Obese or overweight moms could be the reason for heart disease in newborns.
The arterial thickening occurred regardless of the child's weight at birth, according to the paper, published in a specialist edition of the journal Archives of Disease in Childhood.
Doctors in Melbourne asked 23 expectant mothers to take part in the investigation.
Women who were overweight or obese -- defined as having a body mass index (BMI) of 25 or more -- were likelier to give birth to a baby whose aorta wall was thicker (0.06 of a millimetre, 0.02 of an inch) than that of newborns whose mothers were a healthy weight.
The higher the woman's weight, the thicker the wall.
Aorta thickness is considered a benchmark for potential artery clogging.
The findings suggest a mother's weight could affect the risk of cardiovascular disease in her child in later life, said the study.
But further work is needed to explore this suspicion, it added.