A mother's genes, if not passed on, could still affect a child's weight

The portions of a mother's genome that influence a child's weight can include genes not inherited by the child, according to new research.

Researchers at University College London used data from more than 2600 families to look at how the genomes and body mass index (BMI) of parents affect the weight and diet of their children, from birth to age 17. They found that alleles inherited from both parents have an impact, but that the mother's alleles can have an effect even if not inherited, via a phenomenon that researchers have previously referred to as 'genetic nurture' (see BioNews 935).

'Mothers' genetics appear to play an important role in influencing her child's weight over and above the child's genetics,' said Dr Liam Wright, lead author of the study published in PLOS Genetics. 'In addition to the genes mums directly pass on, our findings suggest that maternal genetics are instrumental in shaping the environment in which the child develops, therefore indirectly influencing the child's BMI too.'

Dr Wright and his colleagues used data from the Millennium Cohort Study, a UK birth cohort study of individuals born in 2000-2002. They analysed the genomes of family trios – mother, father and child – as well as BMI, body fat percentage, waist-to-height ratios and reported diet. For the children, measures including BMI were taken at regular intervals throughout childhood.

Using further data from the largest available genome-wide association study on adult BMI, the researchers created polygenic scores for BMI for each family member, and used these to rule out the effects of inherited genetic factors. The researchers also took into account certain non-genetic factors that are known to affect diet and BMI, such as socioeconomic class.

The analysis revealed that after these factors had been taken into account, the mothers' BMI had an influence on the child's weight whereas the fathers' BMI did not. The researchers suggest that this could be the result of 'genetic nurture', where maternal genes influence the way that a mother shapes the environment in which their child develops.

Such nurture can potentially encompass embryonic and fetal development (which occur within the mother's body and are therefore affected by her biology), and also development after birth (inclydinge the food that parents provide and aspects of the way that parents behave).

'This isn't about blaming mothers,' said Dr Wright, but rather is about 'supporting families to make a meaningful difference to children's long-term health'. He added: 'Targeted interventions to reduce maternal BMI, particularly during pregnancy, could reduce the intergenerational impacts of obesity.'

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The meaning, merit and uses of polygenic scores will be discussed at this year's PET Annual Conference, What Does Genomics Mean for Fertility Treatment?.

The conference is taking place in person in London on Wednesday 10 December 2025, with sessions including 'Polygenic Risk, Polygenic Scores, Polygenic Indices: What Are They? What Should Be Done With Them?'. Find out more and register here.