Birth control Population 36 Fertility, Human 30 Contraception 18 Population policy 15 Congresses 13 Family size 12 Religious aspects 10 Family planning 8 Research 7 Study and teaching 7 Abortion 6 Biography 6 Families 6 History 6 Law and legislation 6 Birth control clinics 5 Case studies 5 Communication in birth control 5 Statistics 5 Bibliography 4 Evaluation 4 Catholic Church 3 Contraceptives 3 Marriage 3 Periodicals 3 Population research 3 Prevention 3 Public opinion 3 Sex 3