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Summary Data were collected from 368 Rwanda women, 50 non-lactating and 318 lactating, to determine the effect of lactation on conception rate and the return of menstruation. During lactation the majority of conceptions were found to be delayed by some 15 months, but the family spacing effect was maximal during the first 9 months. By 27 months after delivery the contraceptive effect of lactation can be assumed to have largely disappeared.
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Bönte et al. (1969) studied this question.
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