Ovine hourly fetal urine production: relation to fetal electrocortical activity

OBJECTIVE: Ultrasound studies of hourly urine production rate in human fetuses have suggested that a fall in urine production occurs in state 2F (fetal quiet sleep) secondary to a state-dependent decrease in renal blood flow. We sought to ascertain the relationship between fetal hourly urine production rate and behavioral state in the near-term ovine fetus, a model in which urine production and fetal brain activity can be directly measured. METHODS: Six ewes with singleton pregnancies were prepared with vascular and amniotic fluid catheters. Fetuses were prepared with hindlimb vascular catheters, a bladder catheter, and biparietal ECoG electrodes. After at least 5 days of recovery (ga 130 +/- 2 days; term = 145-150 days), each animal was monitored for a 6-h period. Urine production was measured by draining the bladder catheter through a drop counter and fetal ECoG was continuously recorded (sampling rate of 50 Hz). ECoG activity was analyzed using power spectral analysis and periods of active and quiet sleep identified using both signal amplitude and corresponding 85% spectral edge frequency. RESULTS: Basal fetal arterial pH (7.36 +/- 0.01), pO2 (22.0 +/- 1.2 mmHg) and pCO2 (47.0 +/- 1.6 mmHg) and plasma (295 +/- 2 mOsm/kg) and urine (179 +/- 3 mOsm/kg) osmolalities were within normal ranges. Active and quiet sleep comprised 50 +/- 2 and 43 +/- 1% time, respectively. There was no difference in hourly urine production rate in active sleep (21.4 +/- 9.7 ml/h) and quiet sleep (18.8 +/- 7.7 ml/h). CONCLUSIONS: 1) Hourly fetal urine production rate is independent of ECoG activity state in the near-term ovine fetus. 2) Assuming only minor species differences, ultrasound measurement of human fetal hourly urine production rate can be performed without concern for fetal neurobehavioral state changes.     

Acute maternal rehydration increases the urine production rate in the near-term human fetus

OBJECTIVE: We sought to investigate the effect of a decrease of maternal plasma osmolality produced by hypotonic rehydration on the fetal urine production rate in normal near-term human fetuses. STUDY DESIGN: Twenty-one healthy pregnant women attending the clinic for antenatal care were studied between 37 and 40 weeks' gestation. The fetal urine production rate was assessed by serial measurements of 3 diameters of the fetal bladder. The hourly fetal urine production rate was determined by linear regression analysis of the calculated bladder volumes versus time and was initially determined after a period of 4 hours of fluid deprivation. Thereafter, the women were asked to drink 1 L of water, and the hourly fetal urine production rate was assessed again. The hourly fetal urine production rate was only studied during behavioral state 1F because it is dependent on the behavioral state. The fetal behavioral state was determined by assessment of fetal heart rate, fetal eye movements, and fetal body movements. RESULTS: Successful recordings were obtained in 10 of the 21 women. The hourly fetal urine production rate increased significantly after hypotonic rehydration (P <.02). Compared with the initial hourly fetal urine production rate after 4 hours of fluid deprivation, the hourly fetal urine production rate showed an increase of 63.2% after hypotonic rehydration, from 38.2 +/- 16.3 mL/h to 62.4 +/- 34.6 mL/h (mean +/- SD). After rehydration, the baseline fetal heart rate fell significantly, from 141 +/- 6 to 132 +/- 8 beats/min (mean +/- SD; P =.005). CONCLUSION: The fetal urine production rate is augmented after acute maternal oral hypotonic rehydration after 4 hours of fluid deprivation. The current findings demonstrate that the near-term human fetus can handle such acute changes in fluid osmolality by increasing the urine production rate to maintain its fluid homeostasis. This mechanism implies that changes in maternal plasma osmolality and volume probably play an important role in determining amniotic fluid volume. Therefore the application of maternal hydration for the treatment of oligohydramnios should be further investigated.     

Human and ovine amniotic fluid composition differences: Implications for fluid dynamics

Objective: The ovine model is frequently utilized to extrapolate data regarding fetal and amniotic fluid dynamics to human pregnancy. The ovine amnion is highly vascularized, facilitating intramembranous exchange of water and solutes between the amniotic fluid and fetal plasma. In comparison, the relatively avascular human amniotic membrane may have a reduced potential for intramembranous absorption. In view of these anatomical differences, we hypothesized that comparison of human and ovine amniotic fluid composition would provide insight into differences in the mechanisms of amniotic fluid exchange.

Methods: Amniotic fluid was sampled from 43 patients upon hospital admission, and from 27 ovine ewes at five days following amniotic fluid catheter placement. Both human (32 to 39 weeks' gestation) and ovine pregnancies (125 to 136 days' gestation) were sampled during the last 20% of gestation. Samples were analyzed for osmolality and sodium, potassium and chloride concentrations. The contribution of electrolytes to amniotic fluid osmolality and changes in osmolality and electrolyte composition versus gestational age were assessed by regression and covariance analysis.

Results: Mean (SEM) amniotic fluid sodium concentration (134.6 ± 1.9 vs. 127.1 ± 2.0 mEq/l) was greater and potassium (4.6 ± 0.1 vs. 6.1 ± 0.6 mEq/l) and osmolality (263.9 ± 3.7 vs. 285.1 ± 1.6 mOsm/kg) less in human than sheep. The range of amniotic fluid osmolality was greater in human (223 to 336 mOsm/kg) than in sheep (274 to 298 mOsm/kg). Human amniotic fluid osmolality was highly correlated with amniotic fluid sodium (r = 0.97) and chloride (r = 0.96) while ovine amniotic fluid osmolality was only weakly correlated with amniotic fluid sodium (r = 0.75) and chloride (r = 0.51). The slope of the regression line of amniotic fluid sodium and osmolality was greater for human than for sheep amniotic fluid (P < 0.0001). The percent of amniotic fluid osmolality accounted for by sodium, chloride and potassium concentrations was greater for human (97%) than for sheep (86%; P < 0.0001).

Conclusions: The results suggest that human amniotic fluid osmolality is comprised almost entirely of the major electrolytes while alternative solutes (e.g., fructose) contribute to ovine amniotic fluid osmolality. Extrapolation of fetal and amniotic fluid dynamics from ovine models to humans should incorporate differences in amniotic fluid osmolality and electrolyte composition.     

Unopposed appetite (orexigenic) mechanisms in the near-term ovine fetus: central leptin does not inhibit sucrose ingestion

Objective: Leptin is produced in adipocytes and is present in the term fetus. In the adult, leptin acts centrally to inhibit neuropeptide Y-induced carbohydrate intake. We sought to examine if central leptin alters fetal ingestion of oral sucrose in the near-term ovine fetus.

Methods: Five pregnant ewes and fetuses were prepared with fetal vascular, sublingual and intracerebroventricular (ICV) catheters and esophageal electromyogram electrodes, and studied at 132?±?1 days' gestation (term 145–150 days). Following a 2-h baseline period, 10% sucrose was infused sublingually (0.25?ml/min) for the duration of the study. At time 4?h, leptin (0.075?mg/kg) was administered ICV and fetal swallowing was monitored for an additional 6?h.

Results: During the basal period, fetal swallowing averaged 0.7?±?0.1 swallows/min. Fetal swallowing increased significantly in response to 10% sucrose (1.2?±?0.1 swallows/min; p?<?0.05). In response to ICV leptin, fetal swallowing remained significantly elevated at 2, 4 and 6?h (1.3?±?0.4, 1.4?±?0.3 and 1.5 ±?0.2 swallows/min, respectively; p?<?0.05 vs. control).

Conclusions: These results indicate that central leptin inhibition of sucrose ingestion is not functional in the near-term fetus. We speculate that a leptin-mediated anorexigenic response is not present at birth, such that unopposed appetite stimulatory mechanisms in the newborn may facilitate rapid newborn weight gain despite high body fat levels.     

Effect of Oxymorphone Hydrochloride on Ovine Fetal Heart Rate Variability

In order to determine the effect of the narcotic analgesic oxymorphone hydrochloride (Numorphan, DuPont) on fetal heart rate (FHR) variability, mathematical indices of short-term and long-term FHR variability were determined continuously from R–R intervals of the electrocardiogram in eight chronically instrumented ovine fetuses for 60 min before and after a maternal intravenous bolus of 0.04 mg/kg oxymorphone. The index of short-term variability decreased from 12.7 ± 2.0 during control to 9.7 ± 1.7 during the period from 10 to 30 min after oxymorphone administration during periods of low-voltage, high-frequency electrocortical activity (LVHF ECoG) (P < 0.05). Mean FHR was decreased from 169 ± 8 beats per minute (bpm) during control to 155 ± 7 bpm 30 to 50 min after oxymorphone (P < 0.05). Fetal electrocortical activity was also determined and the decrease in FHR short-term variability occurred despite an increase in the percent time spent in LVHF electrocortical activity from 53 ± 4% during the control period to 74 ± 5% after the oxymorphone injection (P < 0.05). Long-term FHR variability was unaffected by the oxymorphone administration. This study indicates that maternal administration of oxymorphone hydrochloride causes decreased short-term fetal heart rate variability in sheep.     

Saline Amnioinfusion in the Pregnant Ewe: Fetal Responses,Uterine Compliance,and Amniotic Fluid Index

The purpose of this study was to measure the effects of saline amnioinfusion on the fetus, amniotic pressure, and amniotic fluid index (AFI). Eleven chronically catheterized fetal sheep at 137 ± 1 (SE) days gestation received intraamniotically 6 liters of warmed NaCl solution adjusted to be iso-osmotic to amniotic fluid in 1-liter increments at 30-min intervals. Decreases occurred in fetal arterial pressure (4.1 ± 1.0 mmHg, P < 0.01), arterial pH (0.06 ± 0.02, P < 0.001) and p0₂ (2.7 ± 0.8 mmHg, P < 0.01), whereas pC0₂ increased (1.9 ± 0.7 mmHg, P < 0.01). Increases occurred in plasma sodium (2.1 ± 0.5 mEq/L, P < 0.001) and chloride (3.1 ± 0.8 mEq/L, P < 0.001), while potassium decreased (0.3 ± 0.1 mEq/L, P < 0.001). Uterine compliance was 946 ±181 ml/mmHg. The AFI correlated with volume infused (R = 0.85, P < 0.00001). These findings suggest that saline amnioinfusion, although producing minor if any cardiovascular effects in the ovine fetus, significantly alters fetal plasma composition, possibly due to rapid absorption via the intramembranous pathway. In addition, this study demonstrates that the amniotic fluid index increases linearly with the amniotic fluid volume and demonstrates a relatively volume insensitive compliance of the ovine uterus.     

Thromboxane Receptor Blockade Causes Acidemia in the Ovine Fetus

The placenta produces the vasoactive eicosanoids thromboxane and prostacyclin. We hypothesized that fetal administration of SQ 29,548, a thromboxane receptor blocker, would lack direct cardiorespiratory effects in the ovine fetus. Continuous monitoring of maternal and fetal heart rates, blood pressures, and common umbilical artery blood flow was performed in six chronically catheterized pregnant ewes. Serial maternal and fetal arterial blood gases and serum lactates were obtained. After 120 minutes of infusion, a significant decrease in fetal mean arterial pressure and a significant increase in fetal heart rate was observed. A significant decrease in fetal arterial pH (7.41 ± 0.02 to 7.33 ± 0.02), PO₂ (26.8 ± 3.2 to 19.8 ± 3.4), HCO₃^? (27.2 ± 1.5 to 24.9 ± 2.0), and base excess (2.9 ± 1.6 to 0.2 ± 2.3) with a significant elevation in PCO₂ (45.4 ± 2.6 to 50.1 ± 3.3) occurred after 120 minutes of SQ 29,548 infusion. SQ 29,548 infusion caused a significant decrease in common umbilical artery flow, from 249.4 ± 19.4 ml ± min^?1 ·; kg^?1 fetal weight to 178.3 ± 17.9 ml · min^?1 · kg^?1 fetal weight at 120 minutes. Fetal blood lactate levels were significantly elevated from 22.0 ± 3.1 to 54.1 ± 3.8 mg/dL after 120 minutes of SQ 29,548 infusion. Prolonged infusion of SQ 29,548 results in umbilical-placental hypoperfusion and significant alterations in acid-base balance in the ovine fetus.     

Rapid intramembranous absorption of water infused into the ovine allantoic cavity.

OBJECTIVE: Previously we found that water infused into the ovine amniotic cavity was rapidly absorbed into the fetal circulation through the vascularized fetal membranes and fetal surface of the placenta (i.e., the intramembranous pathway). The purposes of this study were to (1) estimate the conductance of the intramembranous pathway from the allantoic cavity and (2) determine if the conductance is adequate to offset the inflow of urine, which may be up to 500 ml/day in the near-term ovine fetus. STUDY DESIGN: Seven chronically catheterized fetal sheep averaging 132 +/- 2 (+/- SE) days' gestation underwent an infusion of warmed distilled water into the allantoic cavity at 6 ml/min. The infusions were continued until steady states were obtained in allantoic and amniotic fluid and in fetal and maternal blood osmolalities. During the steady state the conductance of the intramembranous pathway was estimated as the ratio of osmotic gradient to infusion rate. RESULTS: The allantoic and amniotic fluid and the fetal and maternal blood osmolalities decreased by 188 +/- 14, 36 +/- 8, 13 +/- 2, and 3 +/- 1 mOsm/kg, respectively, at steady state. From the fetal-allantoic osmolality gradients the conductance of the intramembranous pathway was 1.72 +/- 0.14 or 0.53 +/- 0.08 microliter/min/mm Hg/kg fetal weight. Assuming a similar conductance during the preinfusion period, the next volume movement would equal 0.67 ml/min (965 ml/day). CONCLUSIONS: The conductance of the intramembranous pathway in combination with the normal osmotic gradient is sufficient to remove the large volume of fetal urine that may enter the allantoic cavity each day.     

Cerebral Blood Flow and Metabolism in Ovine Fetuses During Asphyxia Resulting in Seizures

Severe fetal asphyxia can cause neurologic damage, but little is known about cerebral oxidative metabolism under these conditions. This study was designed to measure cerebral blood flow and oxygen consumption during severe global asphyxia in fetal sheep, asphyxiated to the point at which seizure activity subsequently occurred. Six sheep were chronically instrumented with fetal electrodes, fetal and maternal vascular catheters, and an adjustable occluder on the maternal common hypogastric artery. Measurements were made of fetal arterial blood gases, blood pressure, heart rate electrocorticogram (ECoG), nuchal muscle electromyogram (EMG), and regional blood flow (radioactive microspheres) during control, and at 30 and 60 min after complete occlusion of the maternal hypogastric artery. The ECoG became isoelectric, and the fetuses developed a marked respiratory and metabolic acidosis, the pH falling to 6.99 ± 0.03, the pCO₂ rising to 73 ± 11 mm Hg, and base excess falling to ?16 ± 1 mEq/L at 60 min of occlusion. Control fetal arterial blood pressure was 52 ± 9 mm Hg and did not change significantly with asphyxia at 60 min. Cerebral cortical blood flow was 127 ± 54 ml/100 g/min at control, and 204 ± 130 ml/100 g/min at 60 min of asphyxia. Cerebral oxygen consumption was 201 ± 50 μM/100 g/min at control, and 76 ± 57 μM/100 g/min at 60 min of asphyxia (P < 0.05), i.e., 45% of control. All 6 fetuses had episodic seizure activity based on ECoG and nuchal EMG activity, beginning 50 ± 47 min after release of the occluder. This seizure activity continued for 24-36 h. This study shows that 60 min of asphyxia associated with suppressed ECoG activity and severe acidosis induced neuronal damage, manifesting as seizure activity, and that this occurred when cerebral oxidative metabolism was reduced to ≤50% of control.     

Effects of narcotic drugs on fetal behavioral activity: acute methadone exposure

The effects of acute methadone exposure on fetal behavioral activity were investigated in 10 unanesthetized fetal lamb preparations. Fetal behavioral activity was interpreted indirectly from the electrocorticogram (ECoG), electromyogram, electrooculogram, blood pressure, heart rate (FHR), and breathing movements (FBMs) of the fetus. Methadone infusion to the mother (5 micrograms/kg/min) resulted in a suppression of all synchronized ECoG activity, and an increase in FBM, FHR, eye movements, nuchal tone, and body movements. Similar effects were observed when 10% of the dose was given directly to the fetus. These results demonstrate that methadone acts directly om the fetus to suppress both quiet sleep and rapid eye movement sleep and results in a "hyperactive" state that has previously been shown to be associated with a 20% increase in fetal oxygen consumption.     

Liver Blood Perfusion as a Possible Instrument for Fetal Growth Regulation

Placental and fetal liver blood perfusions are reduced in intrauterine growth-restricted human fetuses. We hypothesized that changes in fetal liver blood supply can alter fetal growth. In nine ewes with twin pregnancies at a gestational age of 119±2 days, a stent (4 mm) was placed into the ductus venosus of one twin (DV_stent group). Alternatively, in 17 near term sheep with twin (n=11) or singleton (n=6) pregnancies, a DV was blocked with an embolization coil (DV_coil group) for about one week. The cell proliferation rate (pKi-67) was determined in the liver, heart, skeletal muscle, kidneys and placenta. The dilatation or occlusion of the DV did not change placental perfusion on the first day or later after surgery. The liver blood supply was decreased in the DV_stent group by more than half from 499±371 to 278±219 ml min⁻¹ (mean±s.d., n=4), and increased two-fold in the DV_coil group (P< 0.05). The percentage of liver/body weight was decreased from 3.9±0.6 per cent in control twin to 3.0±0.2 per cent (n=3) in the DV_stent group. Occlusion of the DV lead to an increase in the percentage of liver/body weight from 3.4±0.8 per cent to 4.3±0.8 per cent (n=11, P< 0.05). Reduced liver blood supply in the DV_stent group was associated with a decrease of cell proliferation in the liver from 12.43±2.31 to 6.5±0.62 (nuclei μm² 10⁻⁴, n=3, P=0.058), in heart from 1.14±0.03 to 0.93±0.02 (nuclei μm² 10⁻⁴, P< 0.05), and in skeletal muscle from 0.82±0.05 to 0.54±0.01 (nuclei μm² 10⁻⁴, P< 0.05). The increased liver blood perfusion following occlusion of the DV increased cell proliferation sixfold in the liver, (n=9, P< 0.005) and twofold in heart muscle, skeletal muscle and the kidneys (P< 0.05), whereas no significant difference was seen in the placenta. The expression of mRNA for IGF-I and IGF-II in the liver was increased in the DV_coil group. In conclusion, these results suggest that liver blood perfusion can regulate fetal growth.     

Fetal kidney volume and urine production in cases of fetal growth retardation

The amount of amniotic fluid has a close correlation to the function of the fetal renal system. In many cases of fetal growth retardation oligohydramnios is obvious. The aim of this study is the investigation of the hourly fetal urine production rate (HFUPR) and the growth of fetal kidneys during pregnancy in cases of fetal growth retardation and to evaluate the renal participation in the origin of oligohydramnios in cases of growth retardation. In 52 healthy pregnancies and 27 cases with known fetal growth retardation, the volume of the fetal kidneys was measured sonographically and the hourly rate of fetal urine production was determined. Two third of the patients with fetal growth retardation had obvious oligohydramnios. In cases of fetal growth retardation the volume of the fetal kidneys was significantly smaller when compared to the control group, and the volume of fetal urine production was significantly lower. The reduced perfusion of the fetal kidneys in those cases with fetal growth retardation may be the reason for the reduction of the HFUPR. Due to the fact that HFUPR is a dynamical parameter and in close relationship to the perfusion of the fetal kidneys, the identification and measurement of this parameter may help to detect subacute and imminent fetal distress in cases of sonographically proven fetal growth retardation.     

Fetal cerebral and cardiac hemodynamics in postdate pregnancy

Objective: We aimed to determine the fetal cerebro-placental Doppler indices and modified myocardial performance index (Mod-myocardial performance index (MPI)) in this homogenous group of postdated pregnancies.

Methods: A total of 92 singleton pregnant women were included in this prospective study. The study involved three groups; full term control (Group 1, n?=?42, 39 0/7 to 40 6/7 week’ gestation), late term (Group 2, n?=?34, 41 0/7 to 41 6/7 week’ gestation) and post term (Group 3, n?=?16, ≥ 42 0/7 weeks’ gestation). Each participant underwent a Doppler assessment of the fetal umbilical artery (UA), middle cerebral artery (MCA), Mod-MPI. We determined the correlation of the Doppler indices and mod-MPI in patients with unfavorable outcome.

Results: MCA pulcatility indices (PI), cerebroplacental ratio (CPR) values were significantly higher in the control group than those in the late-term and post-term groups (Group 1: 1.63?±?0.3, Group 2: 1.27?±?0.51, Group 3: 1.13?±?0.22, respectively, p?p?Conclusions: Fetal Mod-MPI does not differ in postdate pregnancies with favorable and unfavorable outcome. The monitorization of fetal well-being with CPR may help to clinicians to select patient for expectant management in postdate pregnancies.     

Endocrinological and Biophysical Responses to Further Reduction in Oxygenation Following Sustained Hypoxemia in Fetal Goats

Objective: The purpose of this study was to determine fetal endocrinological and biophysical responses to the further reduction in oxygenation following prolonged nonacidemic hypoxemia in fetal goats.

Methods: Seven further hypoxic experiments were performed after prolonged (24-h) nonacidemic hypoxemia, caused by an infusion of nitrogen into the maternal trachea and by reducing uterine arterial blood flow in four chronically instrumented goat fetuses at 123–131 days' gestation. We measured arginine vasopressin, adrenocorticotropic hormone, cortisol, and cathecolamines as endocrinological parameters. Fetal heart rate, fetal blood pressure, and fetal breathing movement were observed as biophysical parameters.

Results: Fetal arterial pO₂ was significantly decreased from 27.0± 1.2 mmHg (control) to 18.0 ± 0.7 mmHg and 11.3 ± 1.3 mmHg at the end of the prolonged hypoxemia and the further hypoxia, respectively. The further hypoxia induced reductions in fetal heart rate, increases in fetal blood pressure, and a series of gasping. Arginine vasopressin and cathecolamines were elevated significantly by the further hypoxia. Although adrenocorticotropic hormone and cortisol were increasingly elevated, they did not reach a significant level.

Conclusions: Some specific fetal responses—excessive elevations of fetal cathecolamines, arginine vasopressin, accompanied with fetal gasping—were observed during further severe hypoxia.     

Effects of Extracorporeal Membrane Oxygenation (ECMO) on Fetal Lambs

The purpose of this study was to determine the applicability of using ECMO techniques to support fetal oxygenation while maintaining fetal circulation in utero. Extracorporeal membrane oxygenation (ECMO) was applied to four chronically instrumented fetal lambs with the placental circulation intact. Blood was obtained through a catheter (2.5 mm ID) inserted into the right atrium and was returned to the carotid artery after oxygenation (V-A ECMO). The rate of blood flow varied from 200 to 300 mL/min (80-100 mL/kg/min). Compressed air at 2 L/min was used to ventilate the membrane, achieving the mean pO₂ of 36.1 ± 9.5 torr in the blood after the membrane. A positive linear correlation was observed between pre-membrane and post-membrane pO₂. Despite maternal hypoxia experimentally produced by reducing FiO₂ of the mother for 15-35 min, V-A ECMO successfully maintained fetal blood pH and gases within the normal control range. These data indicate that V-A ECMO can effectively oxygenate lamb fetuses     

Fetal heart rhythms during behavioural state 1F

Behavioural state 1F (quiet sleep) of the term fetus is defined on the basis of absence of eye and body movements, and the presence of a specific heart rate pattern (FHRP A), characterized by a stable heart rate with a small oscillation bandwidth. In the present paper the fetal heart rate pattern was studied in 39 enclosed periods with absence of fetal eye and body movements. In 37 periods the heart rate pattern met the criteria of FHRP A. Within FHRP A various distinct types of heart rhythm could be distinguished related to presence of breathing or regular mouthing and complete absence of movements. The bandwidth in the various heart rhythms differed significantly and was largest during breathing movements. During regular mouthing an oscillatory pattern was present with a frequency similar to the frequency of the clusters of mouthing movements. In 2 periods the heart rate deviated from the definition for FHRP A, i.e. a sinusoidal-like rhythm associated with sucking movements. These observations demonstrate the strong association between the fetal heart rate pattern and fetal movements during behavioural state 1F.     

Influence of difficulty of instrumentation with vacuum on the rate of levator ani muscle avulsion identified by 3–4 d transperineal ultrasound

Objectives: Evaluation of the influence of difficulty of instrumentation with vacuum on the rate of levator ani muscle (LAM) avulsions.

Materials and methods: Prospective observational study with 86 nulliparous women with at term gestation who required instrumentation with vacuum to complete fetal extraction. After every delivery, each explorer reported the number of vacuum tractions needed to complete fetal extraction, as well as the subjective complexity of the instrumentation. LAM avulsion rate was assessed by 3D–4D transperineal ultrasound evaluation 6 months after delivery.

Results: Seventy nine cases were evaluated and classified as either “easy” delivery (below three vacuum tractions; n?=?49) or “difficult” delivery (three or more vacuum tractions; n?=?30). No differences in obstetric characteristics were observed between study groups, with the following exceptions: fetal head circumference (34.8?±?2.7 versus 35.2?±?1.1; p?=?.013) and fetal weight at birth (3260?±?421 versus 3500?±?421; p?=?.016). No statistically significant differences between study groups were observed in LAM avulsion rate (36.7 versus 30%) and levator hiatus area (cm²) at rest (18.44?±?3.95 versus 17.75?±?3.90).

Conclusions: The number of vacuum tractions needed to complete fetal extraction is not associated to a higher LAM avulsion rate nor with differences in levator hiatus area.     

Allantoic fluid compositional changes during acute urine drainage in fetal sheep

OBJECTIVE: This study examines the effects of ovine fetal urine drainage, which prevents urine inflow into the allantoic and amniotic cavities, on allantoic and amniotic fluid osmolalities and electrolyte concentrations in an attempt to study solute movement out of the allantoic cavity. METHODS: Nine chronically catheterized fetal sheep at 132 +/- 2 (mean +/- standard error) [SE] days' gestation, with allantoic and amniotic cavity catheters, were studied. Seven animals were studied for 9 hours, with maternal and fetal blood drawn hourly, and amniotic and allantoic fluid sampled for osmolality and electrolyte concentrations. On the second day, seven animals (five from the above group) were studied in the same fashion, except that fetal urine was drained after the first hour. RESULTS: Allantoic and amniotic fluid osmolality increased significantly (13.2 +/- 1.1 (SE) mOsm/kg, P < .0001, 7.5 +/- 1.5, P < .03, respectively) after fetal urine drainage but not sufficiently enough to account for the large amount of fetal urine diverted (217 mL per 8 hours). Fetal (3.1 +/- 0.6, P < .04) and maternal plasma (2.4 +/- 0.5, P < .03) osmolalities increased significantly, and this increase was consistent with the amount of fetal urine drained over the 8-hour drainage period. Allantoic (4.0 +/- 1.7 mEq/L, P < .003) and amniotic sodium (4.2 +/- 1.5 mEq/L, P < .03) and amniotic chloride (3.1 +/- 1.6 mEq/L, P < .04) increased significantly as compared with control animals. CONCLUSION: During the fetal urine drainage period, the increases in allantoic and amniotic fluid osmolalities and electrolyte concentrations confirmed that water left these compartments via the intramembranous pathway. If only water (and not solutes) had left these compartments, then the increase in osmolalities would have been too small to account for the large volume of diverted fetal urine. Therefore, solutes, in addition to water, must leave the allantoic cavity through the intramembranous pathway as no other pathway exists. Furthermore, solute movement through the intramembranous pathway may explain the ability of the fetus to maintain molecular and solute gradients between fluid compartments. Finally, the intramembranous pathway may play an important role in amniotic and allantoic fluid volume regulation and composition.     

Fetal heart rate response to cordocentesis and pregnancy outcome: A prospective cohort

Objective.?To evaluate fetal cardiac response to cordocentesis and whether such changes may affect pregnancy outcome.

Methods.?117 singleton pregnant women requiring percutaneous trans-abdominal cordocentesis were prospectively included. Fetal heart rate was continuously evaluated by ultrasound for 1?min after completion of cordocentesis and intermittently for 20?min more. Fetal and pregnancy outcomes were analyzed by grouping fetal cardiac response to cordocentesis into bradycardia, normal heart rate and tachycardia groups.

Results.?Women included in the study were 30.5?±?4.0 years old and had a gestational age of 23.7?±?2.0 weeks. Fetal blood sample obtained by cordocentesis was 3.1?±?0.8?ml. Fetal heart rate before cordocentesis was 149?±?8 beats per minute (bpm), ranging from 130 to 169 bpm. Fetal heart rate post-cordocentesis was 145?±?30 bpm (from 32 to 175 bpm). The incidence of bradycardia and tachycardia was 10.3% (n?= 12) and 6.0% (n?= 7), respectively. Fetal heart rate returned to normal levels in all cases at ??5 minutes post-cordocentesis. In the tachycardia group, 6 cases had normal pregnancy outcome and one patient was lost to follow-up. In the bradycardia group, we observed two pregnancy terminations, one patient was lost to follow-up and nine were normal outcomes. In the group with normal heart rate (n?=?98), we observed one intrauterine fetal death, nine adverse fetal outcomes, eight pregnancy terminations and nine patients were lost to follow-up.

Conclusions.?Transient fetal tachycardia and bradycardia were uncommon and were not associated with adverse fetal or pregnancy outcomes.     

Fetal anterior abdominal wall thickness between gestational diabetes and normal pregnant women

ObjectivesTo compare fetal anterior abdominal wall thickness (AAWT) between women with and without GDM during third trimester and to determine accuracy of AAWT to predict large for gestational age (LGA) infants.Materials and methodsA total of 250 pregnant women, including 125 women with GDM and 125 women without GDM, were enrolled. Tansabdominal ultrasonographic examinations were performed at 28–30, 32–34 and 36–38 weeks. In addition to standard fetal biometries, AAWT was measured. Patient characteristics and ultrasonographic measurements were compared between groups. Sensitivity and specificity of AAWT for identifying LGA were evaluated.ResultsWhile standard fetal biometries were comparable, mean fetal AAWT in GDM women were significantly higher than those without GDM at 28–30 weeks (2.8 ± 0.8 vs. 2.6 ± 0.6, p = 0.006) and 32–34 weeks (4.0 ± 0.9 vs. 3.5 ± 0.8, p = 0.042). LGA infants had significantly higher fetal AAWT at each time point only in GDM women. Using cut off values of AAWT of ≥2.0, 3.0, and 4.0 mm at 28–30, 32–34, and 36–38 weeks, sensitivity for LGA diagnosis in GDM women were 94.4%, 93.9%, and 89.3%, respectively. The use of abdominal circumference (AC) at >90th percentile showed lower sensitivity but higher specificity, regardless of GDM status. Combination of both measurements increased sensitivity to approximately 90% or higher in every time point, especially among GDM women.ConclusionSignificant increase in fetal AAWT was observed in GDM women at 28–30 and 32–34 weeks. Fetal AAWT significantly increased among LGA infants and had higher sensitivity than AC in identifying LGA during third trimester. In GDM women at 28–30 weeks, AAWT ≥2.0 mm and AC >90th percentile had 97.2% sensitivity for LGA diagnosis.