 In the late 1960s, Singapore was a developing nation and had not yet undergone the demographic transition; though birth rates fell from 1957 to 1970, in 1970, birth rates rose as women who were themselves the product of the postwar baby boom reached maturity.Fearing that Singapore's growing population might overburden the developing economy, Lee started a vigorous "Stop at Two" family planning campaign.Abortion and sterilisation were legalised in 1970, and women were urged to get sterilised after their second child.