The findings are a result of the first ever comprehensive survey into the connection between the age at which women give birth and events they experience in childhood. The research team – led by Daniel Nettle, Reader in Psychology at the University of Newcastle – used complex statistical techniques to analyse data from the National Child Development Study. This study collected extensive data on every child born in one week of 1958 and continues to use personal interviews, medical records and other indicators to form a uniquely comprehensive record of child development. Daniel Nettle and his colleagues used this information to build up a highly detailed picture of the connections between childhood experiences and age of pregnancy.
They discovered that there is a strong connection between certain events – such as short duration of breastfeeding, separation from the mother and lack of paternal involvement – and earlier pregnancies. While previous work has suggested that paternal behaviour affects female development, this is the first time that maternal actions have been examined alongside paternal effects, despite the fact that animal studies have long suggested that maternal care is highly significant.
The next step for the researchers is to discover exactly how these childhood events are related to pregnancy. While it is possible that there is a genetic explanation – for instance, a common gene which is related to a tendency to have children earlier and also to breastfeed for a shorter time – the researchers suggest that it is more likely that these events have a directly causative effect. One possibility is that early pregnancy is an evolutionary adaptation to a difficult upbringing. As the researchers state, the idea is supported by work in other fields: “The idea that harsh conditions very early in life might cause acceleration of reproductive schedules as an adaptive response has developed somewhat independently in behavioural ecology, in developmental biology, and in developmental psychology”.