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[Reduced plasma volume and changes in vasoactive hormones in underweight pregnant women]
1Departamentos de Obstetricia y Ginecología y Pediatría, Escuela de Medicina, Pontificia Universidad Católica de Chile. ssalas@osler.med.puc.cl
Background:
Pregnant women with low weight/height (wt/ht) have lower plasma volume and reduced birth weight than women with normal wt/ht.
Aim:
To explore the hormonal mechanisms involved in these alterations.
Patients And Methods:
Plasma volume, and several hormones related to plasma volume regulation were determined in 24 near term pregnant women with low wt/ht and in 30 with normal wt/ht.
Results:
Newborns's weight, height and ponderal index were reduced in the low wt/ht group. Plasma volume (3042 +/- 101 vs 3631 +/- 101 ml, p < 0.001); plasma renin activity (7.5 +/- 0.9 vs 11.1 +/- 0.9 ng/ml/h, p < 0.01) and aldosterone (428 +/- 47 vs 710 +/- 58 pg/ml, p < 0.001) were significantly reduced in the low wt/ht group. Similar reductions were observed in serum estradiol and progesterone levels. Urinary kallikrein activity (354 +/- 112 vs 824 +/- 134 nmoles/24 h, p < 0.05), 6-keto-prostaglandin F1 alpha (561 +/- 90 vs 1121 +/- 165 ng/24 h, p < 0.05) and thromboxane B2 (110 +/- 29 vs 280 +/- 29 ng/24 h, p < 0.05) were also reduced in low wt/ht women.
Conclusions:
We postulate that the reduced levels of vasoactive hormones observed in pregnant women with low wt/ht may interfere with plasma volume expansion and, in turn, cause low birth weight.