The role of marital sexual abstinence in determining fertility: A study of the Yoruba in Nigeria.

Summary Although sexual abstinence has probably been the single most important factor in restricting human fertility, Western researchers have tended to regard it as a phenomenon mostly found outside marriage. The research reported here was carried out amongst the Yoruba, a sub Saharan people, among whom it is more desirable in terms of social stability to practise female sexual abstinence mainly within marriage, rather than outside it. A similar situation is found widely in tropical Africa. Data are reported from five surveys carried out in 1973-75 in the Changing African Family and Nigerian Family Projects. Three types of marital abstinence are shown to have an effect in reducing fertility: post-natal abstinence (often wrongly described as a 'taboo'), terminal abstinence, and abstinence at other times. Female sexual abstinence is not paralleled by an equal practice of male abstinence, and the main reason for abstinence is to preserve long birth intervals and periods of lactation in a society prone to high rates of infant malnutrition and mortality. It is shown that the Index of Proportions Married (I ( m )) is only one of a number of fertility-weighted indices which can be employed to sub-divide the female reproductive span, and that a complete series of indices adding to unity can be constructed. The duration of lactation and abstinence are found to be related but, because abstinence is traditionally of longer duration, lactation amenorrhoea is of little importance in containing fertility. Married women spend less than half their reproductive lives in periods when sexual relations are possible and marital abstinence is between three and four times more important than delayed marriage in restricting fertility. The period of abstinence is shown to be changing and it is probable that it has never been of an agreed length; the concept of 'natural fertility' is examined in this light. The partial substitution of contraception for the abstinence period is analysed, and the possible effect on fertility considered.