Humans are characterized by long-term stable pair formation compared to other primates, however, cross-cultural studies have shown that pair stability varies between and within populations. The existence of variations in pair stability suggests that in some populations, long-term stable pairs may not be the optimal reproductive strategy. However, it is not clear how pair stability leads to fertility across the individual’s lifespan among high pair-instability populations, especially for women. Therefore, this study examined the relationship between pair stability on women’s fertility across the individual's lifespan in a pair unstable population due to marital norms. This analysis divides the level of pair stability into (1) short-term pair stability: whether the woman changed partners after giving birth /or continued to have children with the same partner and (2) long term: the cumulative number of re-partnerships. As a measure of women’s fertility, 167 birth intervals from 62 women were used in the analysis. A total of 5 months of fieldwork was conducted in Southeast Botswana. Models were fit to R Stan using the brms package. Result: changing partners after childbirth delayed the next childbirth than continuing to have a child with the same partner. Women with 3 or more cumulative re-partnerships had shorter birth intervals than women with 0,1,2 cumulative re-partnerships. Results show that the low pair stability leads to low fertility in short term but not in the long term. Thus, in this group, women’s fertility may improve when the pair is unstable across the lifespan.