Disminución del volumen plasmático y cambios en hormonas vasoactivas en embarazadas de bajo peso / Reduced plasma volume and changes in vasoactive hormones in underweight pregnant women

ABSTRACT

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 ñ 101 vs 3631 ñ 101 ml, p< 0.001); plasma renin activity (7.5 ñ 0.9 vs 11.1 ñ 0.9 ng/ml/h, p< 0.01) and aldosterone (428 ñ 47 vs 710 ñ 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 ñ 112 vs 824 ñ 134 nmoles/24 h, p< 0.05), 6-keto-prostaglandin F1a (561 ñ 90 vs 1121 ñ 165 ng/24 h, p< 0.05) and thromboxane B2 (110 ñ 29 vs 280 ñ 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