Buddhists are concerned with the skilfulness or not of sexual relationships or sexual behaviour. Hence, in Buddhism there is no particular attachment to monogamy, and other types of sexual relationships such as polygamy and polyandry have been practised in Buddhist countries.
Neither is promiscuity considered to be problematic, if all adults are consenting and no unskilfulness, for example in the form of lying, adultery or emotional manipulation, is involved. Some Buddhists practise celibacy or chastity, either short or long term, which can allow them to put more energy into meditation and the work of transformation for the sake of Enlightenment.
Buddhists from non-western countries may say that the number of children that anyone has is determined by fate, and therefore is not something to be tampered with. Hence, they would not use any form of contraception. However, Western Buddhists are more concerned with using contraception that is as ethical as possible; thus, for example, the coil may not be used because it could cause mini-abortions (see also the section on 'birth, babies and motherhood').
Some Buddhists may believe that someone is infertile because of karmic actions in a previous existence, and therefore that infertility treatment would be interfering with the natural series of life events.
For information about the termination of pregnancy, see the section on 'birth, babies and motherhood'.