SAO PAULO -- The birth rate in Brazil has fallen by its fastest rate in nearly three decades after the Zika and microcephaly crisis of 2016.

Brazil's statistics agency said on Tuesday there were 2.79 million births in 2016, a 5 per cent decrease from the year prior.

The birth rate fell by 10 per cent in the northeastern state of Pernambuco, where the Zika virus hit particularly hard.

The virus is spread primarily through mosquito bites and causes babies to be born with abnormally small heads and other severe brain defects. But analysts from the Institute of Geography and Statistics suggested the country's long economic crisis may have also made couples delay plans to have children.

"Those were difficult years. Our research doesn't show whether the reasons for the fall were Zika and the economy, but those are very reasonable possibilities," analyst Klivia de Oliveira said.

Birth rate figures had risen in the six previous years.