Adult sex ratio and declining birth rates in Birhan HDSS rural Ethiopia

The study examined the adult sex ratio and fertility rate at Birhan Health and Demographic Surveillance System (HDSS) in the Amhara region of Ethiopia. Globally, the sex ratio at birth and total population remains stable, with approximately 105.6 boys born for every 100 girls and 101 males born for every 100 females, respectively. Ethiopia's average population sex ratio is 101 males to 100 females. Fertility rates have declined globally since 1950, including in sub-Saharan Africa. Ethiopia's fertility rate decreased from 6.4 in 1990 to 4.6 in 2016. The HDSS monitors health and demographic conditions in both rural and urban areas, providing an updated sampling frame for nested studies. We used both the HDSS and the open cohort data to calculate key indicators, including Crude Birth Rate (CBR), General Fertility Rate (GFR), Total Fertility Rate (TFR), and Adult Sex Ratio (ASR). The study's strength lies in its comprehensive approach to pregnancy screening and birth outcome registration, yielding valuable data beyond traditional surveys. The mid-year population was 72,776, with a higher number of males (38,454) than females (34,322). Among individuals aged 15-24, women comprised 37.4% of the group, resulting in a sex ratio of 167.4 males per 100 females. For the broader reproductive age range (15-50 years), the sex ratio was 125 males per 100 females. In 2022, the TFR was 3.44 children per woman, reflecting a 25.22% decline compared to Ethiopia's national TFR of 4.6 in 2016. Other key fertility indicators also demonstrated notable reductions: the CBR was 19.98 per 1000 population, and the GFR was 104.78 per 1000 women of reproductive age, marking decreases of 37.24% and 32.83%, respectively, from the 2016 national averages. The findings indicate a youthful population with a higher male-to-female ratio, particularly among younger age groups. Fertility rates are notably lower compared to national figures. The decline may be attributed to gendered migration patterns and reduced conception risk among migrants, influenced by improved living conditions in urban areas and temporary separation from partners.