Scientists claim stress during pregnancy can be traced back to the experiences of our ancestors.

Researchers from the University of Lethbridge in Canada were surprised to find that mild to moderate stress during pregnancy had an effect across generations.

As time goes by the effects of stress grew larger with each generation, said Gerlinde Mertz, one of the researchers.

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She noted that previous epigenetic studies focused on the inheritance of DNA methylation signatures. What scientists didn't know is whether microRNAs can be inherited across generation, she explained.

Mertz said their study provides new insights on how stress can influence pregnancy risk and childbirth complications.

She said the findings also have implications outside pregnancy. Scientists believe many complex diseases can be rooted in the experiences of our ancestors.

Mertz believes a better understanding of the mechanisms of inherited epigenetic signatures could predict disease risk and reduce future illness risks.

Epigenetics or the arrangement and expression of one's genes causes these changes due to microRNA, a non-coding RNA molecules that regulates gene expression.

MicroRNA is a small non-coding RNA molecule that has 22 nucleotides. It's an important biomarker of human disease.

Scientists agree further work needs to be done to understand mechanisms that generate epigenetic signatures and how they pass on to each generation.

They believe an extensive knowledge of these mechanisms may prevent preterm pregnancy and cure other diseases.