|PhD ceremony:||Ms R.M. (Renske) Verweij|
|When:||January 31, 2019|
|Supervisors:||prof. dr. M.C. Mills, prof. dr. H. (Harold) Snieder|
|Co-supervisor:||dr. G. (Gert) Stulp|
|Where:||Academy building RUG|
|Faculty:||Behavioural and Social Sciences|
In many Western countries childlessness has been increasing. For example, in the Netherlands, among women born in 1940 only 12% remained childless, while among women born since 1955 more than 17% remained childless.In this dissertation reasons why men and women remain childless are examined. Findings indicate that only a small part of people remain childless because they did not want to have children. Furthermore, the desire to remain childless did not explain why higher educated and working women become mothers less often. An important reason why people remain childless despite the desire to have children is postponement. Dutch men and women expect their first child around the age of 30, and during the life course this age is further increased. Reasons why people increase this age, are not having a partner, permanent contract, full-time job and not owning a house.
Also genetic factors are linked to childlessness. In two genetic studies in this dissertation, using twin methodology and polygenic risk scores, findings showed that genetic differences between individuals partly explain whether people have children. However, genetic and social influences are difficult to distinguish, as genes that relate to having children also relate to the probability to get married, the age at which people get married and education. For this reason, it is important to simultaneously study both genetic and social-environmental influences on childlessness.