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.
The women's body mass was measured, and within seven days of birth, the doctors measured the baby's abdominal aorta, the body's main artery, using ultrasound.
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.