The sex ratio at birth (SRB) in 2019 is 111.5 boys per 100 girls, which is significantly skewed. The SRB in Viet Nam began to increase around 2004, reaching 112 boys per 100 girls after 2010 and has levelled off ever since.

The SRB in Viet Nam is higher than the biological level (104-106 boys per 100 girls), suggesting that in 2019 the number of missing girls is about 45,900. This shortage is equivalent to 6.2% of all female births. The highest SRB is recorded in the Red River Delta, where the SRB is higher in rural areas than in urban areas, at 115.2 and 112.8 boys per 100 girls, respectively. Sex imbalances at birth occur in all wealth quintiles. Over the last 10 years, the SRB of the poorest quintile has increased from 105.2 to 108.2 boys per 100 girls, while the figure for the richest quintile has remained high (112.9 boys per 100 girls in 2019).

Son preference and the need for a son affect the couples’ desire to have additional children. Couples with two children but no son are twice as likely to have an additional child than couples with at least one son. Having an additional child due to son preference is particularly evident in the population group with higher education and better living standards.

Son preference is reflected largely in prenatal sex selection as early as the first parity, with the SRB for the first parity being 109.5 boys per 100 girls and rising for the third and higher parities (119.8 boys per 100 girls). For couples who have already had two daughters, the SRB for the third parity is 143.8 boys per 100 girls. The current sex imbalance at birth will affect the future population structure, causing an excess of young men. Forecasts suggest that, if the SRB remains unchanged, there will be a surplus of 1.5 million men aged 15-49 in 2034, and this figure will increase to 2.5 million in 2059. If the SRB declines rapidly and reaches the normal level by 2039, the male excess for the 15-49 group will still be 1.5 million men in 2034 and 1.8 million in 2059.