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The relationship between breast-feeding and subsequent pregnancy in East Bhutan is examined, against the background of local attitudes to family planning. Ninety-eight mothers who had given birth 30-36 months earlier were interviewed. Semisolid supplementary feeding was introduced at a median age of 3 months. Median total duration of breast-feeding was 28 months, and day and night breast-feeding on demand was continued throughout. Median duration of postpartum amenorrhoea was 12 months, and was associated with the timing of the introduction of supplementary foods. There was a significant association between the occurrence of a subsequent pregnancy and early termination of breast-feeding. The relationships between breast-feeding pattern and pregnancy interval are complex, and their relative influence changes with time. During the first year postpartum, infertility during lactational amenorrhoea is important. During the second year there is a strong negative effect on lactation from the next pregnancy. The only important reason for ceasing to breast-feed within 2 years seems to be a new pregnancy.

This study examines the effects of birth order and interpregnancy interval on birthweight, gestational age, weight-for-gestational age, infant length, and weight-for-length in a sample of 2063 births from a longitudinal study in the Philippines. First births are the most disadvantaged of any birth order/spacing group. The risks associated with short intervals (< 6 months) and high birth order (fifth or higher) are confined to infants who have both attributes; there is no excess risk associated with short previous intervals among lower-order infants, nor for high birth order infants conceived after longer intervals. This pattern is observed for all five birth outcomes and neonatal mortality, and persists in models that control for mother's age, education, smoking, family health history and nutritional status. Since fewer than 2% of births are both short interval and high birth order, the potential reduction in the incidence of low birthweight or neonatal mortality from avoiding this category of high-risk births is quite small (1-2%).

Biological fertility is poorly measured by the number of children born in industrially advanced societies. The time elapsing from when a couple decides to have a child to clinically recognizable pregnancy is a useful alternative. Time to pregnancy can be collected in broad categories in large samples. A model for condensing important information from such data is presented, which fits several large samples of reported waiting times. It is shown that multiparous women conceive more quickly than primiparous women.