An international research team, including the Norwegian Institute of Public Health, has found twelve genes that may help determine why some people have children at an early age, while others remain childless.
More than 300,000 women and men from 63 national cohorts were included in the multi-centre study, which is the largest of its kind. The Norwegian Mother and Child Cohort Study (MoBa) from the Norwegian Institute of Public Health had the largest dataset. The results were published in Nature Genetics.
Researchers looked at the ages of participants when they had their first child and how many children they had during their lives, and compared this data with marker genes. In all, the researchers found twelve genes that play an important role in fertility. Ten of the twelve genes were previously unknown. This is a breakthrough in our understanding of the genetic causes of infertility.
It is the largest study to date that has looked at fertility genes in the entire genome (genetic material). The study is also the first that is large enough to study men’s fertility genes.
“The new findings increase our understanding of the complex relationship between genes and the ability to have children,” says Per Magnus, one of the researchers behind the study and project leader of MoBa.
Magnus stresses that both genes and environment – not to mention individual choices – interact with fertility and infertility.
“Further research is needed before we can use this new knowledge in medical practice,” says Magnus.
There is a trend in the developed world for women to have children later than they did previously. The average age of first birth is now 28 to 29 years in many countries, including Norway. The researchers see a correlation between increased childbearing age, lower fertility and unwanted childlessness.
In Norway today, 24 per cent of 45-year-old men and 13 per cent of 45-year-old women are childless. Scientists have calculated that 48.5 million couples worldwide cannot have children.
“We see that men have lower fertility now, but we do not know enough about the causes, says Magnus.
With this study, researchers can establish that genes play an important role in fertility. Genes may explain up to 50 per cent of the causes in terms of how early or late we have children and how many children are born.
“We need more insight into the genetic causes of infertility. Genetics may prove to be just as important as the sociocultural and environmental factors,” says Per Magnus.
The study involved MoBa researchers Ronny Myhre, Bo Jacobsson, Astanand Jugessur and Per Magnus.
Nicola Barban et al. Genome-wide analysis identifies 12 loci influencing human reproductive behaviour. Nature Genetics 2016.
Source: fhi.no / Norway Today