Son Preference and Third-Birth Interval Comparative Analysis of Polygynous Versus Monogamous Families in Pakistan

Son preference remains a deeply rooted sociocultural phenomenon in Pakistan and plays a critical role in shaping fertility behavior. The study investigates the influence of son preference on fertility behavior, with a specific focus on birth intervals and the sex composition of existing children, within the context of marital structure (monogamous vs. polygynous unions) in Pakistan.

Using nationally representative data from the Pakistan Demographic and Health Survey (2012-2013 and 2017-2018), data are analyzed using Cox proportional hazards regression to assess the timing of subsequent births at parity three and linear regression to measure son preference. The sample size included 100 733 women of reproductive age (15-49 years), of whom 96 975 were in monogamous unions and 3758 were in polygynous unions.

The results demonstrate a persistent and significant son preference in fertility decisions. Women with fewer or no sons are more likely to proceed to another birth, as evidenced by shorter birth intervals. A key finding is that polygynous marriages are associated with both higher son preference and shorter birth intervals compared to monogamous unions. While rural polygynous women exhibit stronger son preference, urban polygynous women tend to have quicker transitions to the next birth. In contrast, monogamous women generally report longer birth intervals and lower levels of son preference, regardless of residence.

The study finds that polygynous marriages are associated with stronger son preference compared to their monogamous counterparts. While rural polygynous women exhibit a stronger son preference than urban polygynous women, the latter have shorter birth intervals.