How both mother and baby genes affect birth weight

The largest research of its kind identifies 190 links between our genetic code and birth weight, two-thirds of which are identified for the first time.

The research looked at genetic information from 230,069 mothers, with the birth weight of one child each, in addition to genetic information and birth weights of 321,223 people across the UK Biobank and the Early Growth Genetics consortium cohorts.

The researchers concluded that the direct effects of a baby’s genes made a substantial contribution to birth weight. However, around one-quarter of the genetic effects identified were from the mother’s genes that were not passed on to the child. Instead, these affected the baby’s growth by influencing factors in the baby’s environment during pregnancy, such as the amount of glucose available.

Understanding the factors that influence birth weight is important because babies who are born very large or small have lower chance of survival and higher later-life risk of metabolic diseases. The research involved more than 200 international researchers from 20 countries and supported by more than 120 research funders.