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Objective: We designed a large prospective study to explore the relationship between maternal homocysteine concentrations and related B vitamins and birthweight., Study Design: Blood was sampled from pregnant women at 30-34 weeks of gestation and their newborn infants (n = 366)., Results: Concentrations of all analytes were higher in umbilical cord compared with maternal samples. Birthweight was related negatively to maternal homocysteine (r = -0.12) but not related to maternal cobalamin, methylmalonic acid, and folate (r = 0.02, r = 0.06, and r = 0.04, respectively). Regression analysis revealed smoking (beta = -313; 95% confidence interval [CI], -479 to -149), gestational age (beta = 150; 95% CI, 118-182), female sex (beta = -146; 95% CI, -256 to -35), and parity (beta = 104; 95% CI, 37-171) as strong determinants of birthweight. Maternal homocysteine, cobalamin, methylmalonic acid, and folate were not determinants of birthweight in multivariate analysis., Conclusion: Maternal homocysteine and B vitamins are not related to birthweight in a multivariate model that was adjusted for potential confounders., (Copyright 2010 Mosby, Inc. All rights reserved.)

Plasma levels of atrial natriuretic peptide (ANP) and the effect of exogenous ANP on renal function have been studied in newborn and adult rabbits. In order to investigate an age difference in responsiveness to ANP, we studied the renal effects of alpha-human ANP (1-28) administered at the same dose per kg body weight in adult and neonatal rabbits. Plasma basal ANP levels were similar in 18 newborn (4- to 11-day-old) compared to 7 adult rabbits (150 +/- 16 and 151 +/- 28 pg/ml, resp.). Eleven newborn and 11 adult rabbits were anesthetized and mechanically ventilated. After a control period, each animal received an hANP loading dose (3 micrograms/kg i.v.), followed by an infusion of 0.3 micrograms/kg/min. Blood gases remained stable throughout the experiment in both groups. Mean blood pressure decreased in newborn (28.5 +/- 0.8 to 26.2 +/- 1.0 mmHg) and adult (92 +/- 3 to 84 +/- 3 mmHg) animals. Percent hANP-induced changes in renal functions in newborn and adult rabbits were, respectively: urine flow rate: -21 +/- 4% and +57 +/- 8%; urinary sodium excretion: +4 +/- 7% and +81 +/- 11%; glomerular filtration rate (GFR): -19 +/- 4% and -4 +/- 6%; renal blood flow (RBF): -22 +/- 4% and -11 +/- 5%. As expected, diuresis and natriuresis increased in adult rabbits. Failure of hANP to increase natriuresis and diuresis in newborn rabbits could be related to the marked decrease in GFR, receptor immaturity and/or interactions with other hormonal systems.