Nephron endowment ranges widely in normal human populations. Recent autopsy studies have drawn attention to the possibility that subtle congenital nephron deficits may be associated with increased risk of developing hypertension later in life. Since modest maternal vitamin A deficiency reduces nephron number in rats, we designed a pilot study to determine the prevalence of maternal vitamin A deficiency in Montreal (Canada) and Bangalore (India) and the usefulness of newborn renal volume as a surrogate for nephron endowment. Among 48 pregnant Montreal women, two (4%) had one isolated mid-gestation retinol level slightly below the accepted limit of normal (0.9 mumol/L), whereas 25 (55%) of 46 pregnant women in Bangalore had at least one sample below this limit. Average estimated retinoid intake was correlated with mean serum retinol in pregnant women from Bangalore. In Montreal where maternal vitamin A deficiency was negligible, we found that newborn renal volume (estimated by renal ultrasonography at 2-6 weeks of age) was correlated with surface area at birth and was inversely correlated with serum creatinine at 1 month. Interestingly, renal volume adjusted for body surface area in Montreal (184+/-44 ml/m(2)) was significantly greater than in Bangalore (114+/-33 ml/m(2)) (p<0.01). Definitive studies are needed to establish whether maternal vitamin A deficiency accounts for subtle renal hypoplasia in Indian newborns. If so, there may be important public health implications for regions of the world where maternal vitamin A deficiency is prevalent.