The Governor of a central Russian province urged couples to skip work today and make love instead.
And if a woman gives birth in exactly nine months time – on Russia's national day on June 12 – she will qualify for a prize.
"It's normally something for the home – a fridge or a television set," Yelena Yakovleva at the Ulyanovsk regional administration press office, said.
"It doesn't matter if it's a girl or a boy."
Regional governor Sergei Morozov told employers to contribute to a Kremlin campaign to boost the birth rate by giving couples today off to have sex.
Russia wants to reverse a trend in which the population is shrinking by about 700,000 people a year as births fail to outpace a high death rate boosted by AIDS, alcoholism and suicide.
This is the third year Ulyanovsk region, famous as the birthplace of Soviet state founder Vladimir Lenin, has dedicated a day to encouraging couples to produce more babies.
Prizes will extend equally to unwed women who produce children on the right day, though the biggest prizes will go to married couples.
On Russia Day this year, a family won a jeep after their fourth baby was born on the holiday.
This year a record 78 babies were born on June 12 at the main hospital in the regional capital of Ulyanovsk, beating the 2006 total of 26, said chief doctor Andrei Malykh.
"The scheme is working. People want the prizes," he said.
A mass wedding and special lessons for children at school on how to deal with having a brother or sister are also planned in Ulyanovsk city, which is about 900km from Moscow.
This week First Deputy Prime Minister Dmitry Medvedev, a possible successor to President Vladimir Putin, said he wanted to stabilise the population at about 142 million by 2015 and boost it back to 145 million by 2025.