The effect of prenatal dietary protein intake on birth weight

Abstract

From 1940 to 1980, protein deficiency was implicated in depressed fetal growth and impaired infant development. Consequently, increasing protein intake in pregnancy was recommended. In 1980, a randomized controlled trial found high protein supplements to be associated with depressed birth weight in low-income pregnant women. The objective of this study was to assess the role of dietary protein during pregnancy in women consuming a self-selected diet. The relation between dietary protein intake and pregnancy outcome was explored in an observational, longitudinal study of low income, mostly urban women. Protein intake was estimated using the average of two 24-hour dietary recalls, the first generally completed between months 4 to 6 and the second in month 8 of pregnancy. Hierarchical multiple regression analyses were conducted, adjusted for maternal, infant and socio-demographic characteristics and for duration of gestation and maternal energy intake. This study found that mean protein intake ≥85 g/day was associated with a 71 g decrement in birth weight ( n = 2163, p = 0.009) compared to intermediate (50–84.9 g/day) average protein intake. About 36% of the women studied reported mean intakes of ≥85 g protein daily during pregnancy, whereas only 12% had low protein intakes (<50 g/day). Thus, the negative effect of high protein intake on birth weight may have considerable public health significance and should not be encouraged.