Chronically reduced amniotic fluid volume (AFV) has serious implications for the fetus including lung hypoplasia and increased risk of umbilical cord compression during delivery. We have developed a model to increase fetal urine production and thereby AFV by creating maternal hyponatremia. We have measured the impact of the model on maternal and fetal blood volume. Five ewes with singleton pregnancies were studied (130±2 d: term=145 d). Ewes and fetuses received hindlimb catheters, while each fetus received a bladder catheter. After 6 days, urine flow rate, and urine and plasma composition were measured at 30 min intervals throughout the study. After a 2 h control period the ewe received a 20 μg bolus of DDAVP. 2L of tap water, followed by a DDAVP infusion (4 ug/h). Maternal hyponatremia was maintained for 3 h by varying the rate of an intravenous infusion of 5% dextrose water (2-5 ml/kg/h). Blood volume was measured at the end of the control and experimental periods using Tc99-labeled red blood cells. Maternal plasma [Na+] decreased from 146+/-1 mEq/l to 140+/-1 mEq/l. Fetal plasma [Na+] followed a similar trend (141+/-1 mEq/l to 134+/-1 mEq/l). Fetal urine flow increased from 1.7+/-0.3 ml/kg/min to 2.6+/-0.4. Maternal blood volume increased from 3462+/-632 to 4014+/-604 ml while fetal blood volume did not change (421+/-94 to 457+/-96 ml). We conclude: (1) Maternal plasma hyponatremia (7 mEq/l) induces both fetal hyponatremia (7 mEq/l) and fetal polyuria (53%); (2) Maternal blood volume expands by 16% while fetal blood volume showed a similar (8%) though non-significant trend.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Molecular Biology