The effect of prenatal dietary protein intake on birth weight Nancy L. Sloan a, *, Sally A. Lederman b , Jessica Leighton c , John H. Himes d , David Rush e a International Programs Division, Population Council, One Dag Hammarskjold Plaza, New York, NY 10017, USA b St. Luke’s-Roosevelt Hospital Center, Department of Medicine, Division of Endocrinology, Nutrition and Diabetes, USA c Community Health Works, New York City Department of Health, USA d Division of Epidemiology, University of Minnesota, USA e School of Nutrition, Sciences and Policy, Departments of Community Health and Pediatrics, Tufts University, USA Received 13 March 2000; received in revised form 15 July 2000; accepted 20 July 2000 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 5 2163, p 5 0.009) compared to intermediate (50 – 84.9 g/day) average protein intake. About 36% of the women studied reported mean intakes of $85 g protein daily during pregnancy, whereas only 12% had low protein intakes (,50 g/day). Thus, the negative effect of high protein intake on birth weight may have considerable public health significance and should not be encouraged. © 2001 Elsevier * Corresponding author. Tel.: 11-212-339-0601; fax: 11-212-755-6052. E-mail address: nsloan@popcouncil.org (N.L. Sloan). Nutrition Research 21 (2001) 129 –139 0271-5317/01/$ – see front matter © 2001 Elsevier Science Inc. All rights reserved. PII: S0271-5317(00)00258-X