Seasonal variation in pre- and postpartum maternal body measurements and infant birth weights.

A sample of 225 rural Taiwanese women were followed longitudinally through two successive pregnancy and lactation periods. Maternal pre- and postpartum weight and skinfold thicknesses and infant birth weights showed considerable seasonal variation. The lowest mean maternal weights, irrespective of pregnancy or lactation status, occurred in the summer months of June, July, and August, when temperatures and rainfall reach their yearly maxima. The lowest mean birth weights were also recorded for the warm, rainy summer months. Furthermore, a disproportionate number of infants weighing less than one standard deviation below the mean birth weight were born between May and October. The observed seasonal variations most probably reflect annual cycles of agricultural activities and food availability.