The reason for this was that the polyandrous females suffered a far lower rate of spontaneous abortion, which occurs when genetic incompatibility between the maternal and paternal genomes results in an immunological conflict between mother and embryo.

ECONOMIST: Polyandry

Russia, of course, still has a seemingly endless series of problems, but the reduction in its abortion rate is yet another reminder that, even in an environment of political stagnation, many social trends are moving in the right direction.

FORBES: Russia's Abortion Rate Is Rapidly Converging With Western Europe's

Given the extensive public health infrastructure and the high literacy and social status of Vietnamese women, experts say the country should not have such a high abortion rate.

CNN: The Abortion Dilemma

The abortion rate in the US is currently 1.2million a year, down from a peak of 1.4million in 1990.

BBC: News | Health | More abortions 'mean less crime'