To determine the effects that pregnancy and infant care have on Embu women's commercial, agricultural and household activities, time use patterns were studied for women at different stages of pregnancy and lactation. Time allocation data were collected from 169 households, visited at random intervals over a year, by use of the spot observations technique. Detailed reproductive data were collected monthly, and household socioeconomic data quarterly. Analyses of Embu women's time use by reproductive status reveal that the demands of pregnancy and lactation require women to decrease the amount of time spent on subsistence agriculture, commercial activities, housework, and tending animals; and to devote more time to resting, breastfeeding, and child care. Agricultural and economic activities are curtailed especially in the 3rd trimester of pregnancy and the 1st period of lactation. This data provide insight into how pregnancy and lactation require women to adjust their time allocation between reproductive and farm labor activities. This decrease in time spent on subsistence agriculture, commercial activities, and household work increases the risk of household economic insecurity during the woman's reproductive years.