Abstract

The Chiang Mai lactation project is a longitudinal field study of human lactation carried out among northern Thai women living in the Sanpatong area of Chiang Mai Province. Its aim was to measure the volume and composition of breast milk transferred from mothers to their infants in the first year postpartum, and to relate it to predictors of milk production, and to the growth of the child. Breast milk and supplementary food intake, and nursing patterns, were recorded over two consecutive 24-hour periods six times during the first year. Samples of breast milk and of supplementary foods were analysed for energy and protein. Supplementary foods were also analysed for bacterial contamination. The growth of the child was measured, and health assessed using a combination of health diaries and examination by a physician. Recruitment to the study was excellent. After recruitment, two subjects left the study area, but otherwise only two dropped out, so complete sets of data covering these variables are available for 58 of the 62 recruited subjects.

PIP:

In the Sanpatong area of Chiang Mai Province in Thailand, 50% of infants began solid foods by 6 weeks old. Further almost 50% of mothers 1 year postpartum used progestogenic injectables. The Chiang Mai Lactation Project consisted of a 1984-1985 cross sectional pilot study with 65 12 month old infants, a 1985-1987 longitudinal study with 62 cases and 55 control infants, and a 1987-1988 follow up study at the end of the 2nd year. The project aimed to relate volume and composition of breast milk transferred from mothers to infants during the 1st year to predictors of milk production and to growth. Health workers measured breast milk intake over 24 hours by test weighing using a K Tron electronic balance during the day. They adjusted this procedure to measure night breast milk intake. The balance weighed foods before and after each feed to measure supplementary food intake. Laboratory staff analyzed breast and supplementary food samples for energy and protein. Health workers recorded to the nearest minute the time when each infant attached to the breast and when it detached to measure duration. Health workers weighed the infants either every 30 or 60 days depending on the study, kept health diaries, and a physical examination to assess growth and health. 90% of the intended sample took part in the cross sectional study. At the end of this study, however, researchers identified other infants during a 2nd survey so the original subject list only covered 75% of the intended sample. They used this double survey procedure to improve identification of births for the longitudinal study which resulted in superb recruitment (only 2 subjects dropped out and 2 left the area). The study resulted in complete sets of data on all subjects. The researchers found the 1 tailed t test at the 5% level to have enough power if the population correlation coefficient was .3-.4.