Vietnam's population is estimated to grow at 1.1 percent this year, down from 1.5 percent last year, the government said.
The population is now recorded at 86.9 million, according to a report on the government website on Monday.
Around 1.24 million children were born in Vietnam this year, down 4 percent from last year. Of 64 cities and provinces, 40 posted declines in the number of children born in 2010.
Among the newborns, the number of third children had by families fell 6 percent compared to 2009, the report said.
The government has set a target of cutting down the population growth by another 0.02 percent in 2011. The average age in Vietnam is expected to rise to 73.2 years, from this year's 72.8 years.
Duong Quoc Trong, director of the General Department on Population, said it is likely that Vietnam will be honored by the United Nations for its population achievements during the past five years.
However, he was quoted in a Tuoi Tre report as saying on Monday that the gender imbalance continued to be of concern this year, with 110 boys born for every 100 girls. In some northern provinces, the ratio was as high as 130/100.