World population grew at a steady rate during the 19th century. However, by the turn of the 20th century, several factors aligned to markedly increase the rate of population growth. Louis Pasteur and Robert Koch's germ theory brought new knowledge of infectious agents and spurred programs to limit their spread — including of use of antiseptics, pasteurization of milk, compulsory vaccination, and improved sanitation. At the same time, mechanization in farming and food processing increased the supply of nutritious foods. These advances coupled to dramatically decrease infant and childhood mortality. The readily observable result was an increase in family size — especially among the urban poor.
The eugenics and birth control movements founded early in the 20th century were different responses to the specter of rampant population growth. Although both movements were involved in reproductive control, each was driven by different objectives and methods. While the birth control movement was concerned with limiting population growth, per se, eugenicists were more concerned with limiting the spread of supposedly dysgenic traits.
Margaret Sanger and leaders of the birth control movement, predominantly women, believed that people should be empowered, by education, to make choices to limit their own reproduction. In a society that frowned on open discussion of sexuality and where physicians knew little about the biology of reproduction, Sanger advocated that mothers be given access to the scientific information needed to thoughtfully plan conception.
Davenport and other eugenic leaders, predominantly men, believed that the state should be empowered, by statute, to control reproduction by whole classes of people they deemed genetically inferior. Eugenicists focused on segregating the "feebly inherited" in mental institutions, ultimately seeking the legal remedy of compulsory sterilization. (They also employed immigration restriction to limit the growth of certain population groups.)
The birth control movement's emphasis on personal choice aligned it somewhat with the "positive eugenics" advocated by Galton. However, many eugenicists regarded birth control as "dysgenic" because it limited births among the intellectual families who practiced it most frequently. Some, including Davenport, felt that contraception would increase sexual promiscuity among the very classes of people they sought to restrict.
Harry Sharp performed the first eugenic sterilization, in1908, and Sanger was arrested in 1913 for opening the first birth control clinic. Although the Supreme Court was quick to uphold the concept of mandated sterilization (Buck v. Bell, 1927), only in 1965 did it uphold a woman's right to seek medical advice on contraception (Griswold v. Connecticut).