Gravidity and parity in postmenopausal American Indian women: the Strong Heart Study

The fertility of a large sample of American Indian women participating in the Strong Heart Study was examined to determine which factors are associated with variation in completed fertility among women in this population. The Strong Heart Study (SHS) is a study of cardiovascular disease (CVD) and its risk factors in American Indians living in Arizona, Oklahoma, and the Dakotas. Data were derived from a baseline examination between 1989 and 1992 of approximately 1,500 men and women, aged 45-74, from each of the 3 SHS centers. A personal interview elicited demographic information, family health history, and information on several life-style variables. A total of 1,955 ever-married, postmenopausal women were considered in these analyses. Women were considered to be postmenopausal if their menstrual cycles had stopped completely for at least 12 months, either because of natural or surgical processes. The average number of pregnancies (gravidity) for all women was 5.9, whereas the mean number of live births (parity) was 5.3. Women living in Arizona (5.6) and the Dakotas (5.8) had higher parity than those in Oklahoma (4.6). Furthermore, there was lower completed fertility in younger women: When American Indian women from all 3 centers were considered together, women born between 1910 and 1919 had a mean parity of 5.3, whereas women born between 1940 and 1949 had a mean parity of 4.0. Although previous research has suggested a relationship between parity and CVD risk factors, no linear associations between CVD risk factors and fertility were indicated in this population. We also examined the relationship of contraception, level of education, and income to fertility. While no significant relationship between contraception and the level of fertility was identified, there was a significant inverse linear relationship of both education and income with fertility. In summary, fertility rates in American Indian women are high, but appear to be decreasing in younger generations. Fertility is higher in those with less education and lower incomes.