Consanguinity as a determinant of reproductive behaviour and mortality in Pakistan

Abstract

To determine the prevalence of consanguineous marriages and estimate the effects of consanguinity on reproductive behaviour and mortality, household and hospital-based surveys were conducted in 11 cities in the Pakistan province of Punjab between 1979 and 1985. The 9520 women interviewed reported 44,474 pregnancies, with data collected on maternal and paternal ages at marriage, abortions/miscarriages, stillbirths and deaths in the first month, at 2-12 months and 2-8/10 years. Six categories of consanguineous marriage were included: double first cousin, first cousin, first cousin once removed/double second cousin, second cousin, bradari (brotherhood) and non-consanguineous. Marriages contracted between spouses related as second cousins or closer accounted for 50.3% of the total, equivalent to an average coefficient of kinship (alpha = sigma piFi) of 0.0280. Unions between close biological relatives were characterized by younger maternal and paternal ages at marriage and reduced spousal age difference, but a longer time to first delivery. Overall, they exhibited greater fertility than non-consanguineous couples. Antenatal and postnatal mortality were assessed by consanguinity and age interval. Consanguinity-associated deaths were consistently higher in the neonatal, infant and childhood periods. The consequences of these outcomes on the health of the present and future generations is assessed.

PIP: There are 20-55% of all unions in Africa and Asia that are marriages between close biological relatives (consanguinity). All major religious groups in Asia, except the Hindus and Sikhs in North India, report consanguineous marriages. In the assessment of the determinants of reproductive behavior and postnatal mortality, retrospective data on 9520 families in 11 cities in Punjab province in Pakistan between 1979 and 1985 were examined. Background variables were age of both partners at age of marriage, spousal age difference, time to first delivery, number of pregnancies, number of abortions/miscarriages, stillbirths, death in the first month, at 2-12 months, and at 2-8/10 years. Consanguinity was defined as marriages between second cousins of closer and included the following: double first cousin, first cousin, first cousin once removed or double second cousin, second cousin, and nonconsanguineous. The results showed that 50.25% of marriages were between second cousins or closer. 37.07% were first cousin marriages, 11.72% were first cousin once removed or second cousin marriages, and .56% were second cousin unions. 33.93% were "bradari" marriages, which denoted fraternal or paternal lines and were classified as nonconsanguineous. Mother's age at first marriage was 18.35 years and father's age at first marriage was 23.28 years for double first cousin unions vs. 19.74 years and 25.97 years, respectively, for nonconsanguineous unions. Spousal age differences were also negatively associated with consanguinity. There were positive associations between mean number of pregnancies and live births and consanguinity. Mortality rose from 16.36% in nonsanguineous pregnancies to 20.09% among second pregnancies, to 22.13% among first cousins, and 38.97% among double first cousins. This findings suggest the expression of harmful recessive genes. Caution is urged in this interpretation because age and socioeconomic status were not controlled. Further data collection and analysis are urgently needed to examine carefully the effects of marriage to a close relative on mortality.