Changes In Amniotic Fluid Volume Research Articles

A prospective observational study to evaluate the association of various maternal risk factors with increasing incidence of term neonatal jaundice

<p><strong><em>Background: </em></strong><em>In our setting majority of the mothers were discharged on postnatal day 3.but over the past few years the NICU admissions also increased prolonging the hospital stay of mothers leading to increase in the hospital acquired infections for both mother and baby. This study was developed in this context. <strong></strong></em></p><p><strong><em>Objectives:</em></strong><em> The present study was performed with the purpose of establishing the incidence of neonatal jaundice in term neonates and the role of the various maternal factors being responsible for exaggerated physiological hyperbilirubinemia in term neonates. <strong></strong></em></p><p><strong><em>Methods: </em></strong><em>Using the NICE gestational age-based phototherapy chart, this study analysed serum bilirubin of the term newborns on their day 2 of life. Total 155 antenatal mothers were taken for study. Associations between maternal risk factors and neonatal jaundice and comparing risk factors in early-term, term, and late-term newborns were assessed using chi-squared or Fisher’s exact tests</em></p><p><strong><em>Results: </em></strong><em>Incidence of neonatal jaundice is 58.1% in this study. Age, BMI, weight gain of the mother had no significant correlation with neonatal jaundice. Blood group incompatibility had a positive corelation (P=.001) Gestational age at the time of delivery determines the neonatal outcome. (P=.001). As gestation advances the neonatal outcomes are better. Hyperbilirubinemia incidence more at 37 -38 weeks when compared to 39 weeks. Maternal comorbidities, amniotic fluid volume changes, mode of delivery didn’t have statistical significance. when new-born factors are considered birth weight, gender growth problems, blood group has no statistical significance whereas dehydration proved to be significant (P=.001). meconium-stained amniotic fluid[P-0.034] were found to be associated with the development of neonatal jaundice.</em></p><p><strong><em>Conclusions: </em></strong><em>The prevalence of jaundice is higher in this study. maternal and foetal blood group incompatibility, gestational age at delivery, meconium-stained amniotic fluid, neonatal dehydration was found to be associated with the development of neonatal jaundice.</em></p>

PREGNANCY IN THE PERIOD OF THE DELTA VARIANT OF CORONAVIRUS DISEASE: SOMATIC AND PERINATAL ASPECTS

The purpose of this study is to investigate the clinical symptoms of the delta variant of the coronavirus disease in pregnant women, and to analyze the course of pregnancy in this period.
 Materials and methods. An assessment of the courses of the coronavirus disease and pregnancy in the period from September to November 2021 was carried out.
 The clinical manifestations of the disease are characterized by moderate severity due to respiratory disorders (86.2%), subfebrile body temperature and weakened breathing (20.6%), accompanied by wheezing (17.2%). A significant proportion of patients (20.6%) require oxygen support due to the respiratory complications. Common laboratory findings include anaemia and lymphopenia (11.5±1.1%), as well as elevated levels of ferritin (123.5±19.1 ng/mg), C-reactive protein (12.9±1.6 mg/l), prothrombin time (12.4±1.4 sec), and D-dimer (0.76±0.04 µg FEU/ml).
 The recommended treatment for this condition includes the administration of antipyretics, LMH (presumably low molecular weight heparin), antibiotics (in the case of bacterial complications), and corticosteroids.
 Pregnant women are particularly vulnerable during the second trimester (II trimester) of pregnancy. This vulnerability is attributed to the rapid growth of the uterus and the subsequent increase in central blood volume, which places additional strain on the cardiovascular system. As a result, the disease tends to have a more severe course during the second trimester compared to the first and third trimesters. Consequently, pregnant patients in the second trimester require hospitalization more frequently.
 Pregnant women with the delta variant of coronavirus disease can demonstrate various obstetric manifestations. These include oligohydramnios (6.8%) and polyhydramnios (3.4%), as well as placental thinning (10.3%) and placental thickening (3.4%). Additionally, moderate preeclampsia (6.8%) and gestational pyelonephritis (10.3%) have been reported. Changes in Doppler parameters such as a decrease in STV (systolic time interval) to 3.3±0.3 ms (in 29% of cases), an increase in PI (pulsatility index) to 0.8±0.05, and an increase in SDS (systolic-diastolic ratio) to 3.3±0.03, as well as an increase in IR (resistance index) to 0.8±0.05 in the umbilical cord artery have been observed. Preterm labour occurs in 6.9% of cases between 34 and 36+6 weeks, and in 3.4% of cases before 34 weeks. Other obstetric complications include primary uterine inertia (13.8%), secondary uterine inertia (10.3%), cephalopelvic disproportion (6.9%), fetal distress (3.4%), bleeding in the third stage of labour (3.4%), and caesarean section (17.2%) due to obstetric reasons.
 Neonates born to mothers with the delta variant of coronavirus disease may exhibit the following manifestations: the Apgar score at 1 minute is generally 7.8 ± 0.4 points, and at 5 minutes it is 8.2 ± 0.2 points; Respiratory functional impairment (10.3%) and low weight for gestational age (6.9%) have been observed, necessitating respiratory support in 6.9% of cases.
 Conclusion: The delta variant of coronavirus disease in pregnant women is characterized by respiratory disorders, tachycardia, hyperthermia, infiltrative lung changes, elevated inflammatory markers, hypercoagulability, and lymphopenia. The disease tends to have a more severe course during the second trimester due to increased cardiovascular and respiratory strain. Obstetric complications, such as changes in amniotic fluid volume and placental thickness, preeclampsia, gestational pyelonephritis, and compensated placental dysfunction, are thought to arise from inflammatory, hypercoagulable, and endothelial changes in the placenta. However, complications during childbirth and the condition of newborns do not appear to be directly related to the maternal disease.

Comparison of Amniotic Fluid Index at Different Gestational Age in Normal Pregnancy

Sonographic assessment of amniotic fluid has formed an integral and important component of pregnancy assessment of fetal wellbeing. Changes in amniotic fluid volume are associated with variable outcome of the fetus. Amniotic fluid index which is an objective means of assessing adequacy of amniotic fluid volume does not only vary with gestational age but also differs from population to population. The study determined the reference values of amniotic fluid index and compared the values with the established ranges throughout gestation in uncomplicated singleton pregnancies among women attending our antenatal care facility. This was a longitudinal prospective assessment of amniotic fluid index in eighty six healthy pregnant women with singleton pregnancies recruited at 20 to 22 weeks of gestation and followed up to 41 weeks and 3 days. The patients recruited at 20 weeks had amniotic fluid measurements at recruitment and 4 weeks apart until 40 weeks gestation. Those recruited at 22 weeks had it also at recruitment and 4 weekly with the last estimation at 41 weeks +3 days. These measurements were plotted against their respective gestational ages. The graph was then analyzed using statistical and graphical packages of SPSS version 21. The study populations mean, 5th and 95th percentiles was documented and discussed appropriately. A total of 414 readings were obtained from 81 subjects who underwent more than 3 measurements. Analysis of the data obtained shows a rising AFI with a mean 28 weeks and, thereafter gradually fell till term. The mean age obtained in the study group compared with that of Caucasians showed statistically significant difference (P=0.014). Also, comparison with Chama et al. showed obvious statistical difference at the lower limit (5th percentile; P=0.007, 50th percentile; P=0.006) but no differences at the upper limit (95th percentile; P=0.726). Amniotic fluid index values appear to be differing in different population. The reference range of AFI used in clinical practice should therefore be based on data obtained from local population.

Regulation of amniotic fluid volume: mathematical model based on intramembranous transport mechanisms.

Experimentation in late-gestation fetal sheep has suggested that regulation of amniotic fluid (AF) volume occurs primarily by modulating the rate of intramembranous transport of water and solutes across the amnion into underlying fetal blood vessels. In order to gain insight into intramembranous transport mechanisms, we developed a computer model that allows simulation of experimentally measured changes in AF volume and composition over time. The model included fetal urine excretion and lung liquid secretion as inflows into the amniotic compartment plus fetal swallowing and intramembranous absorption as outflows. By using experimental flows and solute concentrations for urine, lung liquid, and swallowed fluid in combination with the passive and active transport mechanisms of the intramembranous pathway, we simulated AF responses to basal conditions, intra-amniotic fluid infusions, fetal intravascular infusions, urine replacement, and tracheoesophageal occlusion. The experimental data are consistent with four intramembranous transport mechanisms acting in concert: 1) an active unidirectional bulk transport of AF with all dissolved solutes out of AF into fetal blood presumably by vesicles; 2) passive bidirectional diffusion of solutes, such as sodium and chloride, between fetal blood and AF; 3) passive bidirectional water movement between AF and fetal blood; and 4) unidirectional transport of lactate into the AF. Further, only unidirectional bulk transport is dynamically regulated. The simulations also identified areas for future study: 1) identifying intramembranous stimulators and inhibitors, 2) determining the semipermeability characteristics of the intramembranous pathway, and 3) characterizing the vesicles that are the primary mediators of intramembranous transport.

Correlation Between the Duration of Maternal Rest in the Left Lateral Decubitus Position and the Amniotic Fluid Volume Increase

The purpose of this study was to show the relationship between amniotic fluid volume changes and the duration of maternal rest in the left lateral decubitus position. Pregnant women (n = 34) with an amniotic fluid index between 6 and 24 cm and an uncomplicated singleton pregnancy at 35 to 40 weeks' gestation were included in the study. After the initial amniotic fluid index measurements, the women were instructed to rest in the left lateral position, and the measurements were repeated at 15, 30, 45, 60, 75, and 90 minutes. The amniotic fluid index increased at each sequential interval. Although each amniotic fluid index value was higher than the preceding one, only the 15- and 30-minute values were significantly higher than the preceding measurements (P < .001; P < .01, respectively). At the beginning of maternal rest in the left lateral position, 15 minutes of rest was sufficient to create significant changes (P < .001). However, after 30 minutes of rest, an additional 45 minutes was needed to create a significant amniotic fluid index increase (P < .01). The curve describing the amniotic fluid index increases caused by maternal rest resembled a saturation curve, and the maximum increase in the amniotic fluid volume was projected to be achieved approximately at the end of the second hour of the rest period. The correlation between the duration of maternal rest and amniotic fluid volume changes is not linear. However, maternal rest in the left lateral decubitus position significantly increases the amniotic fluid volume, particularly in the first 30 minutes (maximum increase in the first 15 minutes).

Expression of aquaporin water channels in canine fetal adnexa in respect to the regulation of amniotic fluid production and absorption

Amniotic fluid (AF) is created by the flow of fluid from the fetal lung and bladder and reabsorbed in part by fetal swallowing and partly by the transfer across the amnion to the fetal circulation. Placental water flux is an important factor in determining AF volume and fetal hydration. In addition the fetal membranes might be involved in the regulation of fluid composition. To understand the mechanisms responsible for maintaining a correct balance of AF volume we evaluated the expression of aquaporins (AQPs) in canine fetal adnexa. AQPs are a family of integral membrane proteins permitting passive but physiologically rapid transcellular water movement. The presence of AQP1, 3, 5, 8 and −9 was immunohistochemically assessed in canine fetal adnexa, collected in early, middle and late-gestation during ovario-hysterectomies performed with fully informed owners' consent. Changes in AF volume and biochemical composition were also evaluated throughout pregnancy. Our results show distinct aquaporin expression patterns in maternal and extraembryonic tissues in relation to pregnancy period. AQP1 was localized in placental endothelia, allantochorion, amnion, allantois and yolk sac. AQP3 was present in the placental labyrinth, amnion, allantois and yolk sac. AQP8 was especially evident on the epithelia lining the glandular chambers, the amniotic and allantois sacs. AQP9, a channel highly permeable to water and urea, was observed in epithelia of amnion, allantois and yolk sac. In summary, AQP1, 3, 5, 8 and −9 have distinct expression patterns in canine fetal membranes and placenta in relation to pregnancy period, suggesting an involvement in mediating the AF changes during gestation.

Placental and Membrane Aquaporin Water Channels: Correlation with Amniotic Fluid Volume and Composition

Objectives To assess the role of aquaporins (AQPs) in the regulation of amniotic fluid (AF) volume, we determined AF volume and composition and placental and fetal membrane AQP expression throughout the second half of murine gestation. Methods Pregnant CD1 mice were sacrificed at e10–19 and AF volume and composition determined. Placenta and fetal membranes were screened for AQP gene expression. AQP gene expression was quantified by real-time RT PCR and protein location determined by immunohistochemistry. Changes in AF volume were correlated with AQP expression. Results Both membranes and placenta demonstrated expression of AQP1, -3, -8 and -9. Advancing gestation was associated with increased AF volume from e10 to e16, with a marked decrease in AF volume from e16 to e19. By immunohistochemistry, AQP1 was localized to placental vessels and AQP3 to trophoblast. AF volume was negatively correlated with fetal membrane AQP1 and placental AQP1 and AQP9 expression, and positively correlated with placental AQP3 expression. Conclusion Changes in AQPs with advancing gestation, and their correlation with AF volume, suggest a role in mediating placental and membrane water flow and ultimately AF volume. AQP1 appears to regulate fetal membrane water flow, and AQP3 is a likely candidate for the regulation of placental water flow.

Pre-delivery Changes in Amniotic Fluid Volume and Composition in Sheep

To determine the changes in amniotic fluid (AF) volume and solute concentrations during the last 3 weeks of gestation in fetal sheep with a ligated urachus. AF volume as well as solute concentrations of AF, fetal urine, fetal blood, and maternal blood were measured serially over the last 24 days of gestation in chronically catheterized fetal sheep. Statistical analyses included regression analysis and analysis of variance (ANOVA). Delivery occurred at 145.5 +/- 1.1 (SE) days (n = 11 animals). AF volume averaged 913 +/- 46 mL (n = 119 determinations total from 11 animals) and was unchanged with time when analyzed against either gestational age (P = .9) or time prior to delivery (P = .81). Amniotic osmolality, sodium, chloride, glucose, and calcium concentrations decreased as gestation progressed, while potassium and lactate concentrations increased. Only amniotic lactate underwent a pre-delivery increase in concentration. From multivariate regression, AF solute concentrations correlated positively with fetal blood and urine concentrations and negatively with gestational age. In fetal sheep with a ligated urachus, AF volume does not decrease prior to labor and delivery. This differs from the sharp pre-delivery decrease in AF volume that occurs in rats, mice, and pigs and is similar to the relatively constant AF volume in humans, baboons, and monkeys. Further, pre-delivery changes in AF lactate concentration may reflect the consequences of a low AF volume. Regression analysis suggests that fetal blood and urine independently contribute to AF solute concentrations and that gestational age-specific changes in intramembranous transport also may contribute.

Swallowing, urine flow, and amniotic fluid volume responses to prolonged hypoxia in the ovine fetus

OBJECTIVE: Four days of hypoxia produce an extensive fetal polyuria with little change in amniotic fluid volume in the ovine fetus. We hypothesized that fetal swallowing and intramembranous absorption would increase with prolonged hypoxia to offset the polyuria. STUDY DESIGN: After a 24-hour normoxic period, nine ovine fetuses were subjected to 4 days of hypoxia induced by lowering maternal inspired oxygen content. Seven fetuses were monitored for 5 days as normoxic time controls. Measurements included fetal swallowed volume by a computerized system with Transonic flow probes, urine production by gravity drainage, and amniotic fluid volume by an indicator dilution technique. Data were averaged over 12-hour intervals, and a three-factor repeated-measures analysis of variance was used for statistical testing. RESULTS: During days 2 to 5, arterial oxygen tension was 20.7±1.1 (SE) mm Hg in the normoxic and 13.9±0.8 mm Hg in the hypoxic fetuses ( P<.0001). Urine flow was unchanged over time in the normoxic fetuses and increased gradually from 693±88 to 2189±679 mL per day during hypoxia ( P<.0001). The prehypoxia swallowed volume was similar in the two groups, averaging 447±95 mL per day. Although transiently decreased in eight of nine hypoxic fetuses, the 12-hour average swallowed volumes were not significantly different at any time in the hypoxic versus normoxic fetuses ( P = .62). Amniotic fluid volume increased in the hypoxic fetuses relative to that in the normoxic fetuses (520±338 mL vs −226±136 mL, P<.01), although the increase was small ( P<.01) relative to the excess volume of urine (4269±1306 mL). Estimated intramembranous absorption increased from 209±95 mL per day during normoxia to average 1032±396 mL per day during hypoxia. CONCLUSIONS: The current study supports the concept that prolonged hypoxia produces a progressive fetal polyuria with relatively small changes in amniotic fluid volume. Concomitantly, hypoxia does not induce prolonged changes in fetal swallowing; rather, intramembranous absorption greatly increases, thereby preventing severe polyhydramnios.

P46Differential diagnosis in fetal obstructive uropathy

Case reportA healthy 24‐year‐old secundigravida presented for a routine ultrasound examination at the 11th week of gestation. The scan showed a singleton pregnancy and the crown‐rump length (43.8 mm) was compatible with the gestation calculated from the last menstrual period. The foetal abdomen was distended by the presence of one only cyst (12 × 7.4 mm), compatible with distension of the bladder. There was no other evident abnormality. Amniotic fluid volume was normal for the first trimester despite total urethral obstruction. At 14 weeks still birth was found and the patient delivered three days later. Diagnosis was confirmed at autopsy. Post mortem examination confirmed a phenotypically normal male foetus consistent with 14 weeks gestation and weighing 70 gr. The abdomen was distended and the abdominal wall was thin. Internal examination confirmed the presence of an enlarged bladder. There was urethral atresia, with associated dilatation of the bladder but the ureter and kidneys were normal. Internal genitals were male with normal testicles and penis. Chromosome analysis was performed on foetal skin and karyotype was 46, XY.DiscussionCloacal dysgenesis sequence (CDS) is a rare cause of fetal obstructive uropathy (FOU). The prenatal differentition of CDS from other FOU is important because CDS is not amenable to in utero surgical intervention in the form of vescicoamniotic shounts. Differential diagnosis must be made with pathologies capable of determining cystic lesions localised in the inferior foetal abdomen, such as ovarian cysts, intestinal duplications, Hirschsprung disease, colic dilatation, imperforate hymen with hydrometracolps and megacystes–microcolon syndrome. Accurate prenatal diagnosis can be difficult and requires prolonged serial observations. The above‐mentioned pathologies have characteristics of relative ‘fixity’, while typical imaging of cloaca undegoes variations due to sequential filling in, or repletion, of the liquid contained in the urinary, genital and digestive components of the malformation. Moreover, intestinal obstruction is generally associated with polyhydramnios. In the first trimester diagnosis of cloaca anomalies are very difficult because there are no great changes in amniotic fluid volume and ascites rarely is present; serial examinations are required for enable definition of diagnosis.

Human amniotic fluid mathematical model: Determination and effect of intramembranous sodium flux

Objective: A recently described mathematical model of human amniotic fluid dynamics used known and estimated rates of fetal fluid production (lung liquid and urine) and composition (osmolality) to enable calculation of previously unmeasured routes of amniotic fluid resorption, including fetal swallowing and intramembranous (across the amnion) water flow. This "osmolar" model assumed that only free water resorption occurred across the intramembranous route. We hypothesized that intramembranous flow also may include solutes and electrolytes because significant concentration gradients exist between amniotic fluid and fetal plasma. We used mass balance analysis to determine the direction and magnitude of intramembranous sodium flux and to assess the ability of a newly described "sodium" model to predict changes in amniotic fluid volume in response to changes in intramembranous electrolyte flow. Mathematical modeling was used to predict changes in amniotic fluid volume in response to changes in intramembranous electrolyte flow. Study Design: Model predictions were calculated using published values for human amniotic fluid and fetal urine composition and volume. Ovine studies were used to derive lung fluid volumes and composition. Fetal swallowing and intramembranous flow were independently determined using net amniotic fluid osmolar (osmolality model) and sodium (sodium model) balance. Differences between osmolality and sodium model predictions were normalized to calculate the net intramembranous sodium flux, assuming a net balance of intramembranous osmotic solute flow. Results: Both sodium and osmolality models predicted swallowed volume to be greater than intramembranous flow until 28 to 32 weeks' gestation, after which the relationship reversed. However, the sodium model predicted greater intramembranous flow and lower swallowing rates compared with the osmolality model at all gestational ages. Osmolar mass balance required daily intramembranous sodium flux into the amniotic fluid, which increased with gestational age. Furthermore, assuming stable swallowing and intramembranous water flow, the model predicts that 5% increases or decreases in amniotic fluid solute concentrations caused by intramembranous flux result in polyhydramnios or oligohydramnios, respectively. Conclusion: Sodium and osmolality models demonstrate similarities in determinations of amniotic fluid dynamics. However, mass balance equations demonstrate a net intramembranous flow of sodium into the amniotic fluid under normal conditions. Mathematical modeling suggests that small alterations in daily intramembranous sodium flux may evoke large changes in amniotic fluid volume. (Am J Obstet Gynecol 1998;178:484-90.)

Amniotic fluid volume changes with graded anemia in near term ovine fetuses may be mediated by lactate

Amniotic fluid volume changes with graded anemia in near term ovine fetuses may be mediated by lactate

Physiology of amniotic fluid volume regulation.

Although there are fairly wide variations AFV normally undergoes characteristic changes across gestation in which it increases from 10-20 ml at 10 weeks gestation to average 800 ml at 24 weeks. Little change occurs from then until near term when AFV begins to decrease, and large decreases can occur in postterm pregnancies. Across gestation, 95% of AFVs are within the range of 1/2.57-2.57 times the gestational mean volume and 99% are within the range of 1/3.40-3.40 times the gestational mean. Although there are six pathways in which fluid and solutes can enter and/or leave the amniotic sac, there are only four primary pathways that contribute to AFV during late gestation. These include fetal urine and lung fluid secretion as the two primary sources of fluid, with fetal swallowing and intramembranous absorption as the two primary routes of amniotic water clearance. The intramembranous pathway also appears to be a primary source of amniotic solutes (e.g., sodium and chloride). Although fetal hypoxia has been widely believed to cause oligohydramnios, fetal hypoxic hypoxia and anemic hypoxia both appear to be associated with an increased AFV and polyhydramnios rather than oligohydramnios. It is speculated that the oligohydramnios associated with fetal hypoxia is caused by placental dysfunction in addition to the hypoxia.

Uterine artery blood flow response to correction of amniotic fluid volume

OBJECTIVE: Our purpose was to investigate whether acute alterations of amniotic fluid volume affect uteroplacental perfusion.STUDY DESIGN: Three groups of patients of comparable gestational age were studied in a fetal medicine referral unit: (1) eight pregnancies with severe polyhydramnios because of twin-twin transfusion syndrome undergoing therapeutic amnioreduction, (2) seven with severe oligohydramnios undergoing diagnostic amnioinfusion, and (3) six control women having invasive procedures of similar duration without manipulation of amniotic fluid volume. Color Doppler imaging was used to measure uterine artery impedance index values and quantitative blood flow before and within 15 minutes of the end of the procedure.RESULTS: Quantitative flow measurements increased after amnioreduction (74% median increase of volume flow, range 22% to 329%, p < 0.01) and decreased after amnioinfusion (33% median decrease of volume flow, range 17% to 51%, p < 0.05). Impedance index values increased after amnioinfusion (25% median increase in pulsatility index, range 4% to 71%, p < 0.05) and did not alter with amnioreduction. There were no significant changes in the control group.CONCLUSION: Acute changes in amniotic fluid volume after uteroplacental perfusion. In twin-twin transfusion syndrome amelioration in uterine flow may improve fetal condition and explain in part the success of serial amnioreduction therapy.

Does measurement of amniotic fluid index detect changes in amniotic fluid volume after second-trimester amniocentesis?

The objective of this study was to establish whether variations of amniotic fluid volume induced by second-trimester amniocentesis could be detected by serial measurements of amniotic fluid index. A total of 130 singleton pregnancies undergoing second-trimester amniocentesis for genetic indications were considered. Amniotic fluid index was measured at three different time intervals: 30-60 min before amniocentesis, immediately after the procedure, and 60 min after the procedure. Serial measurements were obtained either by a single operator (n = 55) or by the three independent operators (n = 75). Significantly lower amniotic fluid index values were demonstrated immediately after amniocentesis when compared with the pre-amniocentesis and subsequent measurements in the study design with both the single and multiple operators. No statistically significant changes were found between the first amniotic fluid index measurements and those obtained 1 h after amniocentesis. These results suggest that second-trimester amniocentesis induces a temporary decrease of amniotic fluid volume detectable by serial amniotic fluid index measurements, no longer evident 1 h after the procedure.

Transplacental transfer of cefuroxime in uncomplicated pregnancies and those complicated by hydrops or changes in amniotic fluid volume.

The transplacental transfer of cefuroxime was determined at antenatal fetal blood sampling in a cross sectional study of 78 patients between 15-35 weeks' gestation, 8-138 minutes after a maternal intravenous dose of 750 mg. Mean serum cefuroxime concentration, measured by high performance liquid chromatography, was 7.4 (95% confidence interval (CI) 6.8 to 8.1) mg/l in control fetuses; concentrations in hydropic fetuses were similar (6.2 mg/l, CI 4.7 to 7.7) but in fetuses with oligohydramnios they were significantly lower, (4.9 mg/l, CI 3.6 to 6.2). Antibiotic concentration did not correlate with gestational age and remained unchanged by transfusion of packed red cells. We conclude that (i) fetal serum concentrations of cefuroxime obtained after a maternal dose of 750 mg are only adequate for prophylaxis against organisms with a minimum inhibitory concentration of < 4 mg/l and (ii) transplacental passage of cefuroxime is significantly reduced in the presence of oligohydramnios.

Transplacental, amniotic, urinary, and fetal fluid dynamics during very-large-volume fetal intravenous infusions

With rapid intravenous infusion of very large volumes of isotonic saline solutions into the fetus, the fluid could stay within the fetal body, thereby creating hydrops fetalis, be transferred into the amniotic fluid through the fetal kidneys, thereby creating polyhydramnios, or be transferred across the placenta into the maternal circulation. This study was designed to explore these possibilities. After a 1-hour control period, 10 near-term chronically catheterized ovine fetuses were infused intravenously with 4 L (greater than 100% of fetal weight) of either isotonic saline solution or lactated Ringer's solution over 4 hours. Fetal arterial pressure was significantly elevated by 7 mm Hg throughout the infusion (p less than 0.00001). Venous pressure underwent a transient rise (4.8 mm Hg) at 20 minutes of infusion and remained elevated (2.7 mm Hg) during the rest of the infusion (p less than 0.00001). Fetal urine flow increased by an average of 5.7 +/- 0.4 ml/min throughout the infusion (p less than 0.00001) and accounted for 34.1% +/- 2.6% of the infused volume. Estimated fetal extracellular fluid volume increased by 17.7% +/- 1.8% of the infused volume. Because fetal fluid retention, urine flow, and amniotic fluid volume changes accounted for only half of the infused fluid, the remainder of the infused volume must have crossed the placenta and entered the maternal circulation. Given the above changes in vascular pressures, this requires a filtration coefficient of the placenta 50 to 100 times the previously reported values. Thus we conclude that relatively small changes in fetal vascular pressures dramatically alter the filtration capacity of the ovine placenta and transplacental volume flow.

Normal Amniotic Fluid Volume Changes Throughout Pregnancy

Normal Amniotic Fluid Volume Changes Throughout Pregnancy

Normal amniotic fluid volume changes throughout pregnancy

The purpose of this study was to provide a quantitative characterization of the changes in amniotic fluid volume that occur throughout gestation. From 705 published amniotic volumes for normal pregnancies, we found that after log transformation, amniotic fluid volume had a uniform variability over 8 to 43 weeks' gestation. Thus the 95% confidence interval covered the range of 1/2.57 to 2.57 times the mean volume at any given gestational age. Contrary to expected trends, mean amniotic fluid volume did not change significantly between 22 and 39 weeks and averaged 777 ml, with the 95% confidence interval ranging from 302 to 1997 ml. The data are summarized in nomograms covering 8 to 43 weeks' gestation.

Amniotic fluid volume regulation: basal volumes and responses to fluid infusion or withdrawal in sheep.

To better understand the mechanisms that regulate amniotic fluid (AF) volume, we measured AF volume and the rates of fetal swallowing and urination in 33 pregnant sheep at 124-142 days gestation. In four of five ewes over 9-18 days, the spontaneous changes in amniotic fluid volume correlated positively with urine flow rate and negatively with the rate of swallowing (R = 0.686, P less than 0.01), such that 47% of the AF volume changes could be attributed to changes in rates of urination and swallowing. Following infusion of one liter of isotonic amniotic saline (n = 12) or mannitol (n = 5), AF volume increased 110%, and after 24 h returned to the control value in the saline group but it remained elevated 59% above control in the mannitol group. AF sodium was unchanged following saline infusion but remained reduced following mannitol. Following withdrawal of 61% of AF over 20-40 min, AF volume averaged 51 and 71% of control at 24 and 48 h, respectively, whereas AF sodium was unchanged. Variations in rates of fetal swallowing or urine formation could not explain the entire changes in AF volume following either the volume infusion or withdrawal. These data suggest that AF volume is regulated within a relatively narrow range and fetal urine formation and swallowing together and transplacental fluid flux each appear to contribute equally to the regulation of AF volume.