AMNIOTIC FLUID INDEX AND MATERNAL PLASMA VOLUME SHIFTS DURING 50 MINUTES OF MATERNAL IMMERSION IN DEEP THERMO-NEUTRAL WATER.

Background: Amniotic fluid volume (AFV) is a vital sign of fetal well-being. Maternal plasma volume expansion has been demonstrated to have a role in relieving oligohydramnios. Maternal venous fluid infusion, maternal hydration and maternal water immersion can influence both maternal plasma volume and amniotic fluid volume. A previous study showed that water immersion during the third-trimester of pregnancy is able to maintain higher amniotic fluid index (AFI) levels. Objectives: The present study is aimed at exploring the acute shifts in amniotic fluid index (AFI), maternal haematocrit (Ht) and haemoglobin (Hb) levels, maternal plasma volume and plasma and urine osmolality during deep water immersion and it is aimed at evaluating the relationship between amniotic fluid and maternal plasma changes in healthy singleton pregnancies. Methods: 23 volunteers with low-risk singleton pregnancy were recruited. Ultrasound evaluation of the amniotic fluid index (AFI) was provided and urine samples were received before and after 50 minutes of maternal water immersion in deep (200 cm.) thermo-neutral (29°±1°C) water, performing a swimming-program for pregnant women. Before water immersion (0, basal) plasma sample was collected through venous catheter positioned in the cubital vein; plasma sample was collected at 10° minute (1st sample) and at 45°. minute (2nd sample) of water immersion. Urine specific gravity, haematocrit and haemoglobin levels, plasma glucose, sodium, potassium, albumin, total protein and blood urea nitrogen were determined in all samples. Plasma volume change, plasma osmolality as well as percentage (%x) changes of biochemical analytes were calculated from the obtained data. Statistical analysis with paired t-test and correlation Pearson's test; significance from p=0,05. Results: 428 sonographic measurements of deepest amniotic pocket and 552 biochemical evaluations were performed. Complete data from 20 healthy pregnant women were statistically analysed. AFI increased from mm. 150,5±37,5 (mean±SD) to mm. 182,2±38,2 (p< 0,0001) after 50 minutes water immersion period. Sodium slightly raised in the first 10 minutes from 140,3±3,7 to 141,8±4,5 (mEq/L) (p= 0,05). Haematocrit, haemoglobin, glucose, blood urea nitrogen and albumin decreased in the first 10 minutes and remained lower to the end of the water immersion period. Haematocrit: (basal - first - second sample) 34,4±2,3 - 33,5±2,8 - 33,1±2,4 (p=0,002); haemoglobin (g/dL): 11,8±0,8 - 11,5±1,0 - 11,3±0,7 (p= 0,002); glucose (mg/dL): 82,9±13,1 - 73,0±10,3 - 66,8±7,8 (p<0,001); blood urea nitrogen (mg/dL): 19,1±4,6 - 18,4±4,9 - 17,8±5,2 (p=0,02); albumin (g/dL): 3,52±0,2 - 3,4±3,1 - 3,4±3,0 (p=0,01). Potassium level, plasma osmolality and total protein didn't alter during water immersion. Estimated maternal plasma volume raised from basal 2833,9±340,2 mL to 2869,7±338,6 (p=0,009) and 2889,8±331,9 (p=0,002) after 50' water immersion, with a 106,3±8,2% shift in plasma volume estimated by haematocrit and haemoglobin values. The amount of %AFI changes was significantly correlated to the %Ht changes (r= -0,44; p=0,05), to the %Hb changes (r= -0,52; p=0,01) and to the %plasma volume changes (r=0,54; p=0,01). Conclusion: This study agrees with previous papers to state the rapid increase in plasma volume during maternal acute hydration and water immersion. Modulation in intramembranous absorption could be hypothesized to be the link between maternal plasma volume changes and amniotic fluid volume. Studies demonstrated that low maternal plasma volume expansion and high haematocrit and haemoglobin levels can be used to predict and monitor women at risk for preeclampsia. So, later immersion could be a harmless, available and pleasant way to prevent dehydration and low plasma volume expansion during pregnancy. [ABSTRACT FROM AUTHOR]