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Genetic Variation Influences Family Planning Decisions, Including Family Size

Joanna Lawrence
2nd November, 2016

A team of researchers has discovered that specific DNA sequences are correlated with when women give birth to their first child as well as how many children they have in their lifetime. These genetic factors were also associated with the age of onset for both menstruation and menopause. Environmental and social conditions still play a larger role but the findings may help scientists better understand reproductive behaviors. The details are in a paper that was just published in the journal Nature Genetics. Researchers led by the University of Oxford performed a genomic analysis using 62 separate datasets. The team compared age at first birth (AFB) and the number of children ever born (NEB) with genetic factors. The large-scale study included data from 251,151 individuals for AFB and 343,072 individuals for NEB. The researchers discovered 12 genetic loci (positions on chromosomes) of interest and found that these DNA variants could be used to help predict both AFB and NEB in women. The team identified 24 genes that appeared to play a role in influencing AFB and NEB. Some of the genes have already been studied and linked to fertility, menstruation, age of menopause, and other reproductive factors. Other genes had yet to be studied and their functions are currently unknown. Overall, these genes are responsible for about 1% of the variation in AFB and NEB between women. It’s a small number but significant due to the huge sample sizes and methods of genomic analysis. The authors caution that these genetic variants do not determine family planning choices on their own. Environmental, social, and personal factors play a much larger role. The newly discovered genes influence reproductive behavior enough to be of scientific interest, however, and further studies are planned. The team believes that their findings could even lead to improved fertility treatments in the future if the genes’ roles are discovered. REFERENCE Mills et al. Genome-wide analysis identifies 12 loci influencing human reproductive behavior. Nature Genetics (2016).