<正>Hearings in the British Parliament have provided compelling evidence that the population growth factor in the world’s poorest countries is inhibiting development.Low-resource countries cannot escape from poverty or achieve health security while their birth rates are high.Two hundred million women who do not want a pregnancy do not have access to contraceptive methods,as barriers to family planning are numerous.The countries of East Asia largely overcame these barriers,and a new paradigm for understanding what causes fertility decline provides hope that the demographic barrier to development and health security,including maternal health,can be overcome.