Ann Cartwright's book Parents and Family Planning Services (1970) had become a classic in its field.Originally published in 1976, How Many Children? Dr Cartwright's study of family size and spacing in England and Wales in 1973 is again based on detailed research and analysis, and upon interviews with the mothers and fathers of a random sample of legitimate births in England and Wales.Ann Cartwright discusses the extent to which people have firm intentions about their family structure and the factors which may affect these intentions - work, housing, economic situation, marital relationships and family roles. She describes the part played by contraception, abortion and birth control services in people's achievement of their intentions.A major interest of the study is in changes over time. It attempts to throw some light on the falling birth rate and the relative contributions to this decline of desires for smaller families, different spacing patterns and the use of more effective methods of birth control. Comparisons are made with the earlier study, Parents and Family Planning Services, and a fascinating conundrum emerges: in the later study, parents were using more effective methods of birth control but the proportion of unintended pregnancies had not declined. Possible explanations for this are discussed.