Usefulness of fetal urine production measurement for prediction of perinatal outcomes in uteroplacental insufficiency

Amniotic Fluid Disorders: From Prenatal Management to Neonatal Outcomes

Amniotic fluid volume assessment has become standard in the surveillance of fetal well-being, especially in high-risk pregnancies. Amniotic fluid disorders are a frequent and important topic in fetal and perinatal medicine. However, although important advances have been achieved, many important and challenging questions remain unanswered to date. An abnormally low amniotic fluid volume, referred to as oligohydramnios, has been traditionally considered a possible indicator of placental insufficiency or fetal compromise and is associated with an increased rate of obstetric interventions. An excess of amniotic fluid, referred to as polyhydramnios, may be secondary to fetal or maternal conditions and has been associated with a variety of adverse pregnancy outcomes, especially when it is severe. The ultrasonographic detection of an amniotic fluid disorder should prompt a proper workup to identify the underlying etiology. Data on the association of isolated oligohydramnios or idiopathic polyhydramnios with adverse obstetric and perinatal outcomes are conflicting. While the management of secondary oligohydramnios is usually guided by the underlying condition, the management of isolated oligohydramnios is poorly defined. Similarly, the management of idiopathic and secondary polyhydramnios is not yet standardized. There is an urgent need for randomized clinical trials to provide stronger recommendations on the management of these two common conditions.

Quantification of Fetal Renal Function Using Fetal Urine Production Rate and Its Reflection on the Amniotic and Fetal Creatinine Levels During Pregnancy

Adequate prediction of fetal exposure of drugs excreted by the kidney requires the incorporation of time-varying renal function parameters into a pharmacokinetic model. Published data on measurements of fetal urinary production rate (FUPR) and creatinine at various gestational ages were collected and integrated for prediction of the fetal glomerular filtration rate (GFR). The predicted GFR values were then compared to neonatal values recorded at birth. Collected data for FUPR across different gestational ages using both 3D (N = 517) and 2D (N = 845) ultrasound methods showed that 2D techniques yield significantly lower estimates of FUPR than 3D (p < 0.0001). A power law function was shown to best capture the change in FUPR with fetal age (FA) for both 2D ( F U P R 2 D ( m L min ) = 0 . 000169     FA 2 . 19 ); and 3D ( F U P R 3 D   ( m L min ) =   3 . 21 × 1 0 - 7   FA 4 . 21 ) data. The predicted FUPR based on the observed 3D data was shown to be strongly linearly related (R ² = 0.95) to measured values of amniotic creatinine concentration (N = 664). The FUPR_3D data together with creatinine levels in the fetal urine and serum resulted in median predicted fetal GFR values of 0.47, 1.2, 2.5, and 4.9 ml/min at 23, 28, 33, and 38 weeks of fetal age (50% CV), respectively. These values are in good agreement with neonatal values observed immediately at birth. The derived FUPR and creatinine functions can be utilized to assess fetal renal maturation and predict fetal renal clearance.

Middle Cerebral Artery-to-Uterine Artery Pulsatility Index Ratio and Cerebroplacental Ratio Independently Predict Adverse Perinatal Outcomes in Pregnancies at Term

This study aimed to investigate potential predictors, including the cerebroplacental ratio and the middle cerebral artery (MCA)-uterine artery pulsatility index (PI) ratio, for adverse perinatal outcomes in pregnancies at term. This was an observational, prospective study of recruited pregnancies at term. The data were extracted from the medical records in hospital. An adverse perinatal outcome was set as the primary observational endpoint. The receiver operating characteristic curve was plotted to investigate the predictive and cutoff values of risk factors for adverse perinatal outcomes. Univariate and multivariate logistic regression analyses evaluated independent risk factors (maternal, neonatal, prenatal ultrasound and Doppler variables) for adverse perinatal outcomes. There were 392 pregnancies at term included in the study, with 19.4% experiencing adverse perinatal outcomes. The MCA-uterine artery PI ratio was a good predictor of adverse perinatal outcomes by receiver operating characteristic curve analysis (area under the curve = 0.886, p < 0.001), and the cerebroplacental ratio (odds ratio, 0.42; 95% confidence interval, 0.20-0.93; p = 0.032) and MCA-uterine artery PI ratio (odds ratio, 0.25; 95% confidence interval, 0.16-0.42; p = 0.032) were two independent risk factors for adverse perinatal outcomes by univariate and multivariate logistic regression analyses. Notably, both MCA-uterine artery PI ratio and cerebroplacental ratio are significant predictors of adverse perinatal outcome in pregnancies at term.

Hourly fetal urine production rate in isolated oligohydramnios at term

Objective

The aim of this study was to evaluate the hourly fetal urine production rate (HFUPR) via three-dimensional ultrasonography in women with isolated oligohydramnios and compare with normal pregnant women at term.

Materials and methods

This was a prospective observational cohort study of 112 women from 34 to 40 6/7 weeks’ gestation. They were classified into three groups according to the amniotic fluid index (AFI) and ultrasonographic estimated fetal weight (EFW) as isolated oligohydramnios (defined as AFI below 5% and appropriate EFW corresponding to gestational age) (n = 34) and IUGR (defined as EFW below 5% corresponding to gestational age irrespective amniotic fluid) (n = 17), and normal pregnancy (n = 61). HFUPR was measured using three-dimensional virtual organ computer-aided analysis. Adverse perinatal outcomes in all participants were examined.

Results

There was no significant difference in HFUPR between patients with isolated oligohydramnios and women with normal pregnancies (median, 40.0 mL/h [interquartile range [IQR] 31.0–66.5] vs. 48.6 [31.5–81.2], p = 0.224). HFUPR was significantly decreased in the IUGR group (13.8 mL/h [IQR 10.1–24.8]), compared to the normal pregnancy group (p<0.001) and the isolated oligohydramnios group (p<0.001). HFUPR was significantly decreased in neonates with adverse perinatal outcomes compared to the control (24.7 mL/h [IQR 13.4–47.4] vs. 43.6 [29.8–79.0], p = 0.016).

Conclusion

HFUPR was not decreased in patients with isolated oligohydramnios but was decreased in patients with IUGR when compared to normal controls at term.

Prenatal Use of Sildenafil in Fetal Growth Restriction and Its Effect on Neonatal Tissue Oxygenation-A Retrospective Analysis of Hemodynamic Data From Participants of the Dutch STRIDER Trial

Objective: Sildenafil is under investigation as a potential agent to improve uteroplacental perfusion in fetal growth restriction (FGR). However, the STRIDER RCT was halted after interim analysis due to futility and higher rates of persistent pulmonary hypertension and mortality in sildenafil-exposed neonates. This hypothesis-generating study within the Dutch STRIDER trial sought to understand what happened to these neonates by studying their regional tissue oxygen saturation (rSO₂) within the first 72 h after birth. Methods: Pregnant women with FGR received 25 mg placebo or sildenafil thrice daily within the Dutch STRIDER trial. We retrospectively analyzed the cerebral and renal rSO₂ monitored with near-infrared spectroscopy (NIRS) in a subset of neonates admitted to two participating neonatal intensive care units, in which NIRS is part of standard care. Secondarily, blood pressure and heart rate were analyzed to aid interpretation. Differences in oxygenation levels and interaction with time (slope) between placebo- and sildenafil-exposed groups were tested using mixed effects analyses with multiple comparisons tests. Results: Cerebral rSO₂ levels were not different between treatment groups (79 vs. 77%; both n = 14) with comparable slopes. Sildenafil-exposed infants (n = 5) showed lower renal rSO₂ than placebo-exposed infants (n = 6) during several time intervals on day one and two. At 69-72 h, however, the sildenafil group showed higher renal rSO₂ than the placebo group. Initially, diastolic blood pressure was higher and heart rate lower in the sildenafil than the placebo group, which changed during day two. Conclusions: Although limited by sample size, our data suggest that prenatal sildenafil alters renal but not cerebral oxygenation in FGR neonates during the first 72 post-natal hours. The observed changes in renal oxygenation could reflect a vasoconstrictive rebound from sildenafil. Similar changes observed in accompanying vital parameters support this hypothesis.

Intra-observer repeatability when assessing the foetal urinary bladder volume by the Virtual Organ Computer-aided AnaLysis and SUM-OF-CYLINDERS methods: A pilot study

Introduction

The aim of this study was to compare the intra-observer repeatability when using two different methods for estimating the volume of foetal urinary bladders.

Method

The urinary bladders of 20 foetuses were documented by three-dimensional ultrasound. Standard deviation was compared when the volumes of identical bladder images were repeatedly estimated using the Virtual Organ Computer-aided AnaLysis and the experimental SUM-OF-CYLINDERS methods.

Results

No systematic deviation was found between the estimated volumes when using these two methods. Standard deviation was smaller for the SUM-OF-CYLINDERS compared to the Virtual Organ Computer-aided AnaLysis method (p < 0.0001). In relation to bladder volumes of 5-25 ml, standard deviation was 11-14% for the Virtual Organ Computer-aided AnaLysis and 4-5% for the SUM-OF-CYLINDERS method.

Conclusions

Using three-dimensional ultrasound images adapted for the Virtual Organ Computer-aided AnaLysis method, foetal urinary bladder volumes can also be estimated using the SUM-OF-CYLINDERS method. The SUM-OF-CYLINDERS method employs technical advances which may result in a lower standard deviation and therefore higher intra-observer repeatability.