Vietnam has formally ended its decades-long two-child policy, a step aimed at halting a sharp drop in the nation's fertility rate that is causing concern about its economic and demographic well-being.

It is forbidden to inform parents of the sex of their baby before birth in Vietnam, as well as to perform an abortion for sex-selection reasons, with penalties imposed on clinics that break the law. The sex ratio at birth, though improved, remains skewed at 112 boys for every 100 girls.

The move responded to a record-low birth rate that has persisted below population replacement levels for three years,