Function curve of the membranes that regulate amniotic fluid volume in sheep

Seven singleton 120-day fetal lambs were prepared with a shunt from the lung to the gastric end of the esophagus, a bladder catheter, and multiple amniotic fluid and vascular catheters. The urachus was ligated. Beginning 7 days later, amniotic fluid volumes were determined by drainage, followed by replacement with 1 liter of lactated Ringer (LR) solution. Urine flow into the amnion was measured continuously. In 14 of 27 experiments, amniotic fluid volumes were determined again 2 days after the inflow into the amnion had consisted of urine only and in 13 experiments after the inflow of urine had been supplemented by an intraamniotic infusion of LR solution. Intramembranous absorption was calculated from the inflows and the changes in volume between the beginning and end of each experiment. The relations between absorption rate and amniotic fluid volume, the “function curves,” were highly individual. Urine production during the infusion of LR solution did not decrease, fetal plasma renin activity decreased ( P < 0.001), and amniotic fluid volume increased by 140% [SE (27%), P < 0.005], but the increase in the amniochorionic absorption rate of 411% [SE (48%), P < 0.001] was greater ( P < 0.005) than the increase in volume. Each of the seven fetuses was proven capable of an average intramembranous absorption rate that exceeded 4.5 liters of amniotic fluid per day. During the infusion of LR solution, the increase in the rate of absorption matched the rate of infusion (both in ml/h), with a regression coefficient of 0.75 ( P < 0.001). Thus, even for large amniotic fluid volumes, volume is not limited by the absorptive capacity of the amniochorion, and, at least in these preparations, the position of the function curve and not the natural rate of inflow was the major determinant of resting amniotic fluid volume.

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Inhibitor of intramembranous absorption in ovine amniotic fluid

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00469.2013 ◽

2014 ◽

Vol 306 (3) ◽

pp. R185-R189 ◽

Cited By ~ 10

Author(s):

Robert A. Brace ◽

Cecilia Y. Cheung ◽

Debra F. Anderson

Keyword(s):

Amniotic Fluid ◽

Absorption Rate ◽

Ringer Solution ◽

Fluid Volume ◽

Fetal Membrane ◽

Fetal Sheep ◽

Membrane Stretch ◽

Amniotic Fluid Volume ◽

Urine Production ◽

Fetal Urine

Intramembranous absorption increases during intra-amniotic infusion of physiological saline solutions. The increase may be due partly to the concomitant elevation in fetal urine production as fetal urine contains a stimulator of intramembranous absorption. In this study, we hypothesized that the increase in intramembranous absorption during intra-amniotic infusion is due, in part, to dilution of a nonrenal inhibitor of intramembranous absorption that is present in amniotic fluid. In late-gestation fetal sheep, amniotic fluid volume and the four primary amniotic inflows and outflows were determined over 2-day intervals under three conditions: 1) control conditions when fetal urine entered the amniotic sac, 2) during intra-amniotic infusion of 2 l/day of lactated Ringer solution when urine entered the amniotic sac, and 3) during the same intra-amniotic infusion when fetal urine was continuously replaced with lactated Ringer solution. Amniotic fluid volume, fetal urine production, swallowed volume, and intramembranous absorption rate increased during the infusions independent of fetal urine entry into the amniotic sac or its replacement. Lung liquid secretion rate was unchanged during infusion. Because fetal membrane stretch has been shown not to be involved and because urine replacement did not alter the response, we conclude that the increase in intramembranous absorption that occurs during intra-amniotic infusions is due primarily to dilution of a nonrenal inhibitor of intramembranous absorption that is normally present in amniotic fluid. This result combined with our previous study suggests that a nonrenal inhibitor(s) together with a renal stimulator(s) interact to regulate intramembranous absorption rate and, hence, amniotic fluid volume.

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Ovine fetal adaptations to chronically reduced urine flow: preservation of amniotic fluid volume

Journal of Applied Physiology ◽

10.1152/jappl.1996.81.6.2588 ◽

1996 ◽

Vol 81 (6) ◽

pp. 2588-2594 ◽

Cited By ~ 13

Author(s):

Stephanie E. Mann ◽

Mark J. M. Nijland ◽

Michael G. Ross

Keyword(s):

Amniotic Fluid ◽

Plasma Osmolality ◽

Urine Osmolality ◽

Urine Flow ◽

Fluid Volume ◽

Fetal Plasma ◽

Arterial Blood ◽

Amniotic Fluid Volume ◽

Fetal Urine ◽

Ovine Fetal

Mann, Stephanie E., Mark J. M. Nijland, and Michael G. Ross.Ovine fetal adaptations to chronically reduced urine flow: preservation of amniotic fluid volume. J. Appl. Physiol. 81(6): 2588–2594, 1996.—Adequate amniotic fluid (AF) volume is maintained by a balance of fetal fluid production (lung liquid and urine) and resorption (swallowing and intramembranous flow). Because fetal urine is the principle source of AF, alterations in urine flow and composition directly impact AF dynamics. Intra-amniotic 1-desamino-8-d-arginine vasopressin (DDAVP) is rapidly absorbed into fetal plasma and induces a marked fetal urinary antidiuresis. To examine the effect of intra-amniotic- DDAVP-induced fetal urinary responses on AF volume and composition, six chronically prepared ewes with singleton fetuses (gestation 128 ± 2 days) were studied for 72 h after a single intra-amniotic DDAVP (50-μg) injection. After DDAVP, fetal urine osmolality significantly increased at 2 h (157 ± 13 to 253 ± 21 mosmol/kg) and remained elevated at 72 h (400 ± 13 mosmol/kg). Urinary sodium (33.0 ± 4.5 to 117.2 ± 9.7 meq/l) and chloride (26.0 ± 2.8 to 92.4 ± 8.1 meq/l) concentrations similarly increased. AF osmolality increased (285 ± 3 to 299 ± 4 mosmol/kgH2O), although there was no change in fetal plasma osmolality (294 ± 2 mosmol/kg). Despite a 50% reduction in fetal urine flow (0.12 ± 0.03 to 0.05 ± 0.02 ml ⋅ kg−1 ⋅ min−1at 2 h and 0.06 ± 0.01 ml ⋅ kg−1 ⋅ min−1after 72 h), AF volume did not change (693 ± 226 to 679 ± 214 ml). There were no changes in fetal arterial blood pressures, pH,[Formula: see text], or[Formula: see text] after DDAVP. We conclude the following. 1) Intra-amniotic DDAVP injection induces a prolonged decrease in fetal urine flow and increases in urine and AF osmolalities. 2) Despite decreased urine flow, AF volume does not change. We speculate that, in response to DDAVP-induced fetal oliguria, reversed intramembranous flow (from isotonic fetal plasma to hypertonic AF) preserves AF volume.

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Measurement of fetal urine production to differentiate causes of increased amniotic fluid volume

Ultrasound in Obstetrics and Gynecology ◽

10.1002/uog.7519 ◽

2009 ◽

Vol 36 (2) ◽

pp. 191-195 ◽

Cited By ~ 6

Author(s):

S. M. Lee ◽

J. K. Jun ◽

E. J. Lee ◽

J. H. Lee ◽

C.-W. Park ◽

...

Keyword(s):

Amniotic Fluid ◽

Fluid Volume ◽

Amniotic Fluid Volume ◽

Urine Production ◽

Fetal Urine

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RELATIONSHIP BETWEEN FETAL URINE PRODUCTION AND AMNIOTIC FLUID VOLUME IN NORMAL PREGNANCY AND PREGNANCY COMPLICATED BY DIABETES

BJOG An International Journal of Obstetrics & Gynaecology ◽

10.1111/j.1471-0528.1977.tb12556.x ◽

1977 ◽

Vol 84 (3) ◽

pp. 205-209 ◽

Cited By ~ 61

Author(s):

L. C. Otterlo ◽

J. W. Wladimiroff ◽

H. C. S. Wallenburg

Keyword(s):

Amniotic Fluid ◽

Normal Pregnancy ◽

Fluid Volume ◽

Amniotic Fluid Volume ◽

Urine Production ◽

Fetal Urine

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Renal and amniotic fluid responses to umbilicoplacental embolization for 20 days in fetal sheep

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.273.3.r1094 ◽

1997 ◽

Vol 273 (3) ◽

pp. R1094-R1102 ◽

Cited By ~ 7

Author(s):

M. L. Cock ◽

R. Harding

Keyword(s):

Amniotic Fluid ◽

Fluid Volume ◽

Partial Pressure Of Oxygen ◽

Kidney Weight ◽

Fetal Sheep ◽

Amniotic Fluid Volume ◽

Urine Production ◽

Body Weights ◽

Fetal Urine ◽

And Control

We determined the effects of placental insufficiency induced by umbilicoplacental embolization on fetal renal function and amniotic fluid volume and composition. Pregnant ewes underwent surgery at 115 +/- 2 days after mating (term approximately 147 days) for implantation of fetal vascular, bladder, and amniotic sac catheters. We studied five fetuses from 120 to 140 days during umbilicoplacental embolization and six control fetuses. Umbilicoplacental embolization reduced fetal arterial partial pressure of oxygen from 24.1 +/- 0.5 mmHg (pretreatment) to 14.6 +/- 0.2 mmHg. Fetal body weights were reduced to 80% of control values. Urine production and glomerular filtration rate in treated fetuses were significantly lower than in controls at 135 days of gestation. Amniotic fluid volume was not different between embolized and control animals. Fetal urine production in treated fetuses, when adjusted for body weight, was not different from that in control fetuses. We conclude that, in fetal growth restriction, reduced kidney weight, rather than hypoxemia per se is responsible for reduced urine production, which, if severe and prolonged, may contribute to oligohydramnios.

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Amniotic fluid volume dynamics

Fetal and Maternal Medicine Review ◽

10.1017/s0965539500000486 ◽

1991 ◽

Vol 3 (2) ◽

pp. 89-104 ◽

Cited By ~ 23

Author(s):

William M Glibert ◽

Thomas R Moore ◽

Robert A Brace

Keyword(s):

Amniotic Fluid ◽

Fluid Volume ◽

Perinatal Morbidity ◽

Fluid Removal ◽

Embryonic Tissues ◽

Amniotic Fluid Volume ◽

Urine Production ◽

Fetal Urine ◽

Fluid Volume Regulation ◽

The Moment

From the moment of implantation until delivery some 37 weeks later, the human embryo or fetus is surrounded by fluid. Initially this fluid is a transudate from maternal and embryonic tissues which provides nutrients for the growing embryo. Starting in early pregnancy, the fetal kidneys begin to contribute substantial quantities of urine to the amniotic fluid volume. At mid pregnancy, when the skin becomes keratinized, the kidneys become the main source of amniotic fluid. Fetal swallowing is the main route of amniotic fluid removal. Although fetal urine production and swallowing have been studied in both human pregnancy and animal models, the knowledge from these investigations is not sufficiently extensive to explain overall amniotic fluid volume regulation. None the less, it is clear that the amniotic fluid is in a dynamic, ever-changing state. The production rate of the fetal urine in the human fetus at term (800–1200ml/day) is sufficient to replace completely the entire amniotic volume every 12–24 hours1. While the fetus is producing large volumes of urine, the volume of amniotic fluid is normally maintained within a very narrow range. Deviations from the normal range are often associated with significant perinatal morbidity and mortality.

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Sonographic Assessment of Amniotic Fluid Volume using Single Deepest Pocket (SDP) among Igbo Women with Uncomplicated Singleton Pregnancies.

10.33798/ajmas2019/00265. ◽

2019 ◽

Vol 2 (1) ◽

pp. 1-18

Author(s):

Chijioke Okeudo ◽

B.U. Ezem

Keyword(s):

Amniotic Fluid ◽

Gestational Age ◽

Cross Sectional Study ◽

Fluid Volume ◽

Singleton Pregnancy ◽

Cross Sectional ◽

South Eastern ◽

Amniotic Fluid Volume ◽

The Mean ◽

Singleton Pregnancies

Background: The amniotic fluid is fundamental for proper fetal development and growth. Ultrasound visualization of the amniotic fluid permits both subjective and objective estimates of the amniotic fluid. Objective: The objective of this study was to determine the reference values of normal single deepest pocket (SDP) – upper and lower limits, mean SDP and variation of the SDP with gestational age among Igbo women of South-Eastern Nigeria extraction carrying uncomplicated singleton pregnancy. Methodology: This was a prospective cross sectional study involving 400 women carrying uncomplicated singleton pregnancies and who were sure of the date of the first day of their last menstrual period. The single deepest pocket / maximum vertical pool were determined once at presentation at the hospital.. The study was conducted from January 1st to December 31st 2015. The second author carried out all the scanning. The SDP was obtained. Results: The womens’ mean and median ages were the same at 28 years. The gestational age range of the pregnancies was 14-41 weeks. The mean SDP was 5.8cm, while the 5th and 95th percentiles were 3.3cm and 8.5cm respectively. There was no difference in the mean SDP in both term and preterm. There was irregular but continuous rise of mean SDP to a peak of 6.8cm at gestational age of 39 weeks. In conclusion, the participants had a mean SDP of 5.8cm. There was also a positive correlation between SDP and Gestational age. We therefore recommend a longitudinal study to assess perinatal outcome and abnormal amniotic fluid volume among Igbo women of South-Eastern Nigeria. Key words: Single Deepest Pocket, Uncomplicated Singleton Pregnancy, Igbo Women.

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