Rest versus heavy work during the last weeks of pregnancy: influence on fetal growth.

The influence of rest versus hard work on fetal growth at the end of pregnancy was assessed prospectively in a population of women who normally work hard during pregnancy. A group of 554 women living in Kalima area (Central Zaire) was admitted for rest in a maternity village for a median duration of 22 days. Self-selection, age, parity, number of living children, socio-economic status, maternal weight and height and gestational age were controlled for. Energy intake estimated in a sample of women in the maternity village and a sample of those staying at home was similar. Protein intake was found to be higher in the resting women. The duration of rest had a strong influence on birth-weight and length in the newborn females but to a lesser extent in the newborn males. There was a 7.5-fold decrease in the rate of low birth-weight in girls when the duration of maternal rest was greater than 21 days. In boys the low-birthweight rate remained unchanged. Although this sex difference could not be explained it is concluded that, in developing countries, avoidance of heavy work can help to raise birthweight and perhaps reduce perinatal mortality.