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Transplacental supply of mannose and inositol in uncomplicated pregnancies using stable isotopes.
OBJECTIVEThe aim of this study was to determine relative contributions of transplacental flux vs. fetal production for inositol and mannose in normal term pregnancies.
STUDY DESIGNSeven term uncomplicated pregnancies undergoing cesarean section were infused with (13)C- and (2)H-labeled isotopes of glucose, inositol, and mannose until a steady state was achieved. Maternal and fetal concentrations of labeled and unlabeled glucose, mannose, and inositol were measured using gas chromatography/mass spectroscopy. The fetomaternal molar percentage excess ratio was calculated for each glucose, mannose, and inositol.
RESULTSThe fetomaternal molar percentage excess ratio of mannose in the fetal artery (F(artery)/M) was 0.99 [97.5% confidence interval (CI), 0.91-1.07] and in the fetal vein (F(vein)/M), 1.02 (97.5% CI, 0.95-1.10). Both were not significantly different from 1.0, consistent with transplacental supply. The fetomaternal ratios for glucose were similar to mannose (fetal artery, 0.95; 97.5% CI, 0.84-1.15; and fetal vein, 0.96; 97.5% CI, 0.85-1.07). The fetomaternal ratio for inositol was significantly less than 1.0 (fetal artery, 0.08; 97.5% CI, 0.05-0.12; fetal vein, 0.12; 97.5% CI, 0.06-0.18), indicating little transplacental flux and significant fetal production.
CONCLUSIONIn normal term pregnancies, fetal mannose and glucose concentrations are dependent upon maternal transplacental supply. Fetal inositol is not dependent upon transplacental supply.
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The Journal of clinical endocrinology and metabolism 97:7 2012 Jul pg 2497-502
Pub Type(s)Clinical Trial
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't