Socioeconomic variations in female fertility impairment: a study in a cohort of Portuguese mothers

OBJECTIVES: This study aimed to assess the association of socioeconomic conditions with female fertility impairment among women who delivered a live birth. DESIGN: Cross-sectional analysis. SETTING: Population-based birth cohort (Generation XXI) assembled in 2005/2006 from five public maternity units in Porto Metropolitan Region, Northern Portugal. PARTICIPANTS: 7472 women aged 18 or more with spontaneous conception and no male diagnosis of infertility were recruited and interviewed immediately after birth with structured questionnaires. EXPOSURES OF INTEREST: Maternal education, occupation and income were recorded as proxy indicators of social conditions. OUTCOME: Impaired female fertility, defined as women who had unsuccessfully tried to conceive for over a year. DATA ANALYSIS: Multivariate logistic regression models were fitted to estimate the association between each socioeconomic indicator and impaired female fertility, stratified by previous pregnancy experience and adjusted for age, pregnancy planning and behavioural characteristics. RESULTS: Among primigravidae, 7.7% (95% CI 6.8% to 8.6%) presented impaired fertility and the prevalence was 9.6% (95% CI 8.7% to 10.6%) in multigravidae. In crude analysis, we found women with impaired fertility to be older, less educated, more likely to have planned the current pregnancy and to be overweight/obese; they had similar levels of income or occupation. In multivariate models, a significant independent association between educational level and female fertility impairment remained among primigravidae (OR (95% CI) vs ≤6 schooling years: 7–9: 0.85 (0.54 to 1.34); 10–12: 0.34 (0.21 to 0.54); >12: 0.24 (0.14 to 0.40), p(trend)<0.001) but not in multigravidae. CONCLUSIONS: This study shows that education might be important in understanding female fertility impairment, particularly among first-time pregnant women. It also points out that the association is not totally explained by other sociodemographic and lifestyle characteristics that have been previously found to be important to disclose this relation.