Life-Course Relationship between Socioeconomic Circumstances and Timing of First Birth in a Birth Cohort

Objectives This study examines the influence of socioeconomic circumstances in childhood (childhood SES) and adulthood (adult SES) on timing of first birth by age 37. Methods A longitudinal study of a 1972-1973 New Zealand birth cohort collected information on socioeconomic characteristics from age 3-32 and reproductive histories at 21, 26, 32 and 38; information on first birth was available from 978 of the original 1037. Relative Risks (RR) and 95% Confidence Intervals (CI) were calculated using Poisson regression to examine first live birth prior to age 21, from 21-25, from 26-31, and from 32-37, by socioeconomic characteristics at different ages. Results Overall, 68.5% of men had fathered a child and 75.9% of women had given birth, by age 37; with overall differences in parenthood to age 31 for men, and 37 for women evident by childhood SES. While parenthood by age 20 was strongly associated with lower childhood SES for both sexes, first entry into motherhood from 32-37 was more likely with higher adult SES at age 32 (RR = 1.8, 95% CI 1.1-3.0 for medium and RR = 1.9, 95% CI 1.1-3.3 for high compared with low). Education also differientated age at parenthood, with those with higher education more likely to defer fatherhood past age 31, and motherhood past age 25 followed by a period of increased likelihood of motherhood for women with higher levels of education from age 32-37 (RR = 1.4, 95% CI 0.87-2.2 and RR = 1.7, 95% CI 1.1-2.6 for medium and high respectively compared with low). Conclusions SES varies across the lifecourse, and SES at the time has the strongest association with first births at that time. Low childhood SES drives adolescent parenthood, with resulting cumulative differences in parenthood past age 30. Those with more education and higher adult SES are deferring parenthood but attempt to catch up in the mid to late thirties.