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To better understand problems during pregnancies at present, we should consider experiences of our ancestors, a new research has suggested. 

The study involving four generations of rats, showed that inherited  epigenetic effects of stress could affect pregnancies for generations. 

Researchers wanted to know how preterm births are influenced by stress. Preterm birth is one of the leading causes of neonatal death and often leads to health problems later in life. Researchers examined the length of pregnancies in rats because in general there is hardly any variation between them. 

 "We show that stress across generations becomes powerful enough to shorten pregnancy length in rats and induce hallmark features of human preterm birth. A surprising finding was that mild to moderate stress during pregnancy had a compounding effect across generations. Thus, the effects of stress grew larger with each generation," said Gerlinde Metz, senior author of the article. 

According to researchers, these changes are due to epigenetic -  the arrangement and expression of our genes. They further added that epigenetic changes are due to microRNA (miRNA) - non-coding RNA molecules that play a role in regulating gene expression.

"Previous epigenetic studies have mainly focused on inheritance of DNA methylation signatures. What we didn't know was whether microRNAs, which are important biomarkers of human disease, can be generated by experiences and inherited across generations. We have now shown that maternal stress can generate miRNA modifications with effects across several generations. I think this is an interesting feature of our manuscript," Gerlinde Metz added. 

Researchers said further works needed to be done to understand the mechanisms that generate these epigenetic signatures and that how they are passed down from generation to generation. 

"Preterm births can be caused by many factors, in our study we provide new insights into how stress in our mothers, grandmothers and beyond could influence our risk for pregnancy and childbirth complications. The findings have implications outside of pregnancy, in that they suggest that the causes of many complex diseases could be rooted in the experiences of our ancestors. When we better understand the mechanisms of inherited epigenetic signatures, we can predict disease risk and potentially reduce the future risk of illness," said Metz.

The research has been published in the journal BMC Medicine.