Has fertility declined from mid-1990s to mid-2000s?

Objective: To assess changes in self-reported fertility from the mid-1990s to the mid-2000s.

Design: The study is a retrospective population-based study.

Setting: The study applied a dataset from two cross-sectional surveys conducted in the mid-1990s and some 10 years later, inviting all women in a county in Norway.

Population: Women aged 50-59 years enrolled in either survey constituted two cohorts. Data on 4468 women in the first survey (Cohort 1940) and 4951 women in the latter survey (Cohort 1950) were collected by structured questionnaires.

Main outcome measures: Prevalence of fertility, infertility with subcategories subfertility and involuntary childlessness, as well as childlessness was estimated and compared between the surveys. Possible sociodemographic and lifestyle predictors of fertility were assessed at different points in time.

Results: Fertility declined over the two successive surveys; 87.8% of the women in Cohort 1940 were fertile compared with 84.2% of the women in Cohort 1950 (p = 0.000). The prevalence of infertility increased over time due to an increase in subfertility from 7.8 to 10.6% (p = 0.000). The level of education increased with time, as did at-risk alcohol consumption and smoking, and these factors were adversely associated with fertility. The proportion of childless women increased across surveys (p = 0.004) but relatively fewer women were involuntarily childless in Cohort 1950 than in Cohort 1940 (p = 0.543).

Conclusion: Fertility, measured at 10-year intervals, declined significantly. The decline in fertility was related to changes in subfertility. Adjustments for sociodemographic and lifestyle factors did not fully explain the decline in fertility.