The aim of this article is to determine whether the age of a woman at first birth is associated with treatment for high blood pressure (HBP) later in life. Baseline data for 62,914 women were sourced from the "45 and Up Study," an observational cohort study of healthy aging in Australia. These women had given first birth between the ages of 18 and 45 years. Odds ratios and 95% confidence intervals for the association between age that a woman gave first birth and treatment for HBP were estimated using logistic regression. Data were stratified by current age (<60 and ≥60 years) and adjusted for demographic and lifestyle factors. There was a significant association between age at first birth and present day HBP. Older age at first birth was associated with a lower likelihood of HBP in women aged 25 to <35 years and 35 to 45 years at first birth (in women currently <60 years) and 35 to 45 years at first birth (in women currently ≥60 years of age), compared with women aged 18 to <25 years at first birth, adjusting for demographic and lifestyle factors. Women who were older when they gave first birth had lower odds of treatment for HBP compared with women who were younger when they gave birth to their first child. The contribution of a woman's pregnancy history, including her age at first birth, should be discussed with a patient when assessing her risk of HBP.