[Age, desire for children and probability of pregnancy in The Netherlands].

Objective: To investigate the relation between the age of women and their probability of conceiving, and to analyse the factors that influence the age at which couples desire to have their first child.
Method: A national survey among women between the ages of 25 and 49. A random sample of 8050 households were approached. In these households 3295 women between the ages of 25 and 49 answered a short questionnaire about planning of the first pregnancy and fertility. Also sociodemographic data were gathered.
Results: There was little variation in probability of conceiving between the ages of 20 and 28; around 65% to 70% after 6 months, just below 90% after 12 months and about 93% after 2 years. The pregnancy rate after 6 months started to decrease after the age of 33, while pregnancy rate after 1 and 2 years decreased gradually from the age of 28 to 75% and about 80% respectively at the age of 35. The year of birth of the woman (the factor 'time') was the most important factor influencing the age at which couples desire their first child. In addition demographic factors particularly a high level of education, and furthermore a high professional level and a high level of family income were associated with the desire to have the first child at a relatively late age.