Timing Of Delivery

researchers have considered timing of delivery primarily determined by the mother’s genes and environmental factors. Now, a new international genetic study led by researchers from Denmark’s Statens Serum Institut (SSI); and the iPSYCH Consortium has identified a link between the baby’s own genes and the timing of delivery.

The research, which involved the University of Exeter, has just published in Nature Communications. Dr. Rachel Freathy; from the University of Exeter Medical School, said: “They had like to thank all the mothers and babies in the Exeter Family Study of Childhood Health and the Bristol-based ALSPAC study. Their data made important contributions to this work. The findings represent a significant step towards better understanding of the timing of birth; especially as they show that the genes of the baby play a role, and not just those of the mother.”

In the study, the researchers started by analyzing genetic information from 84,689 children; from 20 different cohorts in eight countries. “The study was not based on any specific hypothesis. They looked at all the chromosomes and investigated more than 7.5 million genetic variants,” said Senior Scientist Bjarke Feenstra from SSI, who co-directed the study.

Timing of delivery

In a small area on chromosome 2, the researchers discovered a clear statistical association; between common genetic variant in the babies and the timing of delivery. “The therefore proceeded to investigate the association in an additional 9,291 children from Norway, England and Finland. This time they looked specifically at this small area of chromosome 2; and were able to confirm the same association,” said Bjarke Feenstra.

By looking at genetic variants in this area, the researchers discovered that the children; divided into three groups that differed slightly in terms of their genetics. The children in the first group were, on average; born approximately nine hours earlier than the children in the second group, who themselves were born an average of nine hours earlier than the children in the third group.

Bjarke Feenstra said: “The results cannot used to predict time of delivery. However, the important message is that they have now established with great certainty that genetic variation at this particular place in the fetal genome has a biological effect on the duration of pregnancy; small as it may be. This new knowledge will be an important stepping stone in the efforts; to better understand the biology behind how delivery initiated.”

Group of genes

Biologically, this small area on chromosome 2 is particularly interesting as it harbors a group of genes of the so-called interleukin-1 family that produce inflammatory cytokines. In the days and hours leading up to delivery, these cytokines are known to play a central role in the activation of the uterus, detachment and rupturing of the fetal membranes, ripening of the cervix, and initiation of contractions.

“They know that the baby sends a signal to its mother when it is fully developed and ready born. The new discovery in our study is that they seem to have found a genetic switch that can more or less turn up the volume of this signal and thereby influence whether a child is born slightly earlier or later,” said Bjarke Feenstra.

Further studies are needed to understand the effects of the identified genetic variants and to unravel the molecular mechanisms leading to shorter or longer duration of pregnancy. Both preterm and post term birth are detrimental to the health of the newborn. Better understanding of the biological processes influencing the timing of delivery may eventually help prevent preterm or post term birth.