They are from a study on what determines fertility in Portugal by the Fundação Francisco Manuel dos Santos (FFMS) and independent foundation in partnership with the National Institute of Statistics and coordinated by the University of Évora.

According to the document, which is based on a survey carried out in 2013 and which recalls that Portugal has among the world's lowest fertility rates, there is a clear tendency to postpone having children. The average age at which men have their first child is 31.5 while it is even lower for women.

At 30, this age is 4.5 years higher than the average that prevailed in the 1990s.

Half of those surveyed expected to have two children and one quarter said they foresaw only one. The survey also concluded that in general people want to have more children than they actually do.

Factors that lead to the postponement of having children include the extension of period of studies, delayed entry to the labour market, instability in relationships or the lack of one, delays in leaving the parental home, believing that having children is not essential for personal realisation and believing that it is preferable to have fewer children in order to give them better opportunities.

The study notes that the later people have their first child the greater the probability that they will end up only having the one.