Normal amniotic fluid volume across gestation: Comparison of statistical approaches in 1190 normal amniotic fluid volumes

Vaginal fluid index - The fifth amniotic pocket

OBJECTIVE

The forebag is a pocket of amniotic fluid preceding the fetal presenting part. Herein we describe the feasibility of transvaginal measurements of the forebag and assess its correlation with the standard amniotic fluid index (AFI).

METHODS

A prospective study was carried out between January 2019 and July 2020. Eligible cases were women with singletons, vertex presentation, and normal AFI at term. We assessed the implementation and acceptance of a novel process in the clinical practice setting. Feasibility was assessed by using transvaginal ultrasound to measure the three orthogonal planes of the forebag. The vaginal fluid index (VFI) was defined as the volume composite of the three orthogonal planes. Correlations of the forebag measurements with both AFI and maximal vertical pocket were then calculated.

RESULTS

In total, 292 out of 305 (95.7%) women were enrolled. All participants completed both transabdominal and transvaginal ultrasound, of which the vaginal pocket was demonstrated in 266 (91.1%) cases. We found significant correlations, in both nulliparas and multiparas, between the vaginal pocket measurements and the VFI to both the AFI and maximal vertical pocket measurements (R = 0.38, P < 0.001; R = 0.3, P < 0.001, respectively).

CONCLUSION

We introduced a new ultrasound variable, the VFI, with a high feasibility rate. This may provide invaluable information for future decision making around the time of delivery.

A biological classification of Huntington's disease: the Integrated Staging System

The current research paradigm for Huntington's disease is based on participants with overt clinical phenotypes and does not address its pathophysiology nor the biomarker changes that can precede by decades the functional decline. We have generated a new research framework to standardise clinical research and enable interventional studies earlier in the disease course. The Huntington's Disease Integrated Staging System (HD-ISS) comprises a biological research definition and evidence-based staging centred on biological, clinical, and functional assessments. We used a formal consensus method that involved representatives from academia, industry, and non-profit organisations. The HD-ISS characterises individuals for research purposes from birth, starting at Stage 0 (ie, individuals with the Huntington's disease genetic mutation without any detectable pathological change) by using a genetic definition of Huntington's disease. Huntington's disease progression is then marked by measurable indicators of underlying pathophysiology (Stage 1), a detectable clinical phenotype (Stage 2), and then decline in function (Stage 3). Individuals can be precisely classified into stages based on thresholds of stage-specific landmark assessments. We also demonstrated the internal validity of this system. The adoption of the HD-ISS could facilitate the design of clinical trials targeting populations before clinical motor diagnosis and enable data standardisation across ongoing and future studies.

Controlled amnioreduction for twin-to-twin transfusion syndrome

Background:

Twin-to-twin transfusion syndrome (TTTS) is a severe condition causing preterm delivery, fetal death, and neurodevelopmental disorders. This study presents a data-based controlled amnioreduction (AR) protocol composed of sequential amniodrainage in treatment of TTTS.

Methods:

A total of 18 procedures were performed in 11 TTTS pregnancies at 17 to 34 weeks of gestation. The amniotic pressure was measured along with sequential removal of the amniotic fluid, 500 mL each step. The umbilical artery systolic/diastolic (S/D) ratio for each twin was measured pre- and post-AR. Long-term neurodevelopmental outcomes of all TTTS survivors were evaluated from parental answers to a phone survey.

Results:

The amniotic pressure decreased exponentially with the increased volume of removed amniotic fluid until a plateau was obtained. Changes of the S/D ratio between pre- and post-AR procedure did not reveal a clear tendency. The survival rate was 86.4% although 91% of all twins were at Quintero stage III. Long-term neurodevelopment outcomes in the 19 surviving twins were 68.4% optimal, 26.3% suboptimal, and 5.3% abnormal.

Conclusion:

The controlled AR procedure resulted in a relatively high rate of twin survival with favorable long-term neurodevelopment outcomes.

Amniotic Fluid Volume Assessment: Eight Lessons Learned

Actual AFV can be determined by a dye-dilution technique or be directly measured at cesarean. This allows investigators to correlate estimated and actual AFVs. Lessons learned by assessing the relationship of estimated to actual AFVs. 1) Ultrasound estimates normal actual AFVs well, but abnormal AFVs poorly. 2) Quantile regression is a better statistical methodology to create a normal AFV curve across pregnancy. 3) There is no difference in the accuracy of the subjective (visualization without measurements) compared with the objective (visualization with measurements) technique in identifying normal and abnormal AFVs. 4) Color Doppler use leads to the over-diagnosis of oligohydramnios. 5) Intravenous hydration increases actual AFVs. 6) The estimation of AFV can be done with the transducer held perpendicular to the floor or perpendicular to the uterine contour. 7) The single deepest pocket should be used for identifying low AFVs. 8) The AFI should be used for identifying high AFVs.

How to read a fetal magnetic resonance image 101

Accurate antenatal diagnosis is essential for planning appropriate pregnancy management and improving perinatal outcomes. The provision of information vital for prognostication is a crucial component of prenatal imaging, and this can be enhanced by the use of fetal MRI. Image acquisition, interpretation and reporting of a fetal MR study can be daunting to the individual who has encountered few or none of these examinations. This article provides the radiology trainee with a general approach to interpreting a fetal MRI. The authors review the added value of prenatal MRI in the overall assessment of fetal wellbeing, discuss MRI protocols and techniques, and review the normal appearance of maternal and fetal anatomy. The paper concludes with a sample template for structured reporting, to serve as a checklist and guideline for reporting radiologists.

Physiology of intra-abdominal volume during pregnancy

A total of 580 pregnant and 50 puerperal women were included in this cross-sectional study to assess the physiological changes that allow women to adapt to a chronic increase in intra-abdominal pressure during pregnancy. The volume of the uterus, intra-abdominal volume (IAV), visceral and subcutaneous fat was calculated. During pregnancy, the IAV increases up to 1.5 times. Changes in IAV until 24 weeks present a linear relationship (5.2%); thereafter, changes become exponential and, at 40 weeks, IAV increases by 61%. This fact is exclusively related to the progressive growth of the foetus and to the increase in uterine size. At term, the IAV reserve is exhausted, becoming equal the anteroposterior and transverse diameters of the abdomen.In conclusion, the adaptive capabilities of IAV related to the foetal growth are limited by the IAV reserve. The reserve capacity of the IAV and tensile properties of the abdominal wall can be estimated by the dynamics of the anteroposterior and transverse abdominal diameters.IMPACT STATEMENTWhat is already known on this subject? A causal relationship between intra-abdominal hypertension and the development of adverse obstetric and perinatal outcomes has been suggested. Nevertheless, the role of this condition as a leading cause of systemic dysfunction during pregnancy remains unrecognised and underestimated.What do the results of this study add? This study assesses the dynamics of IAV in uncomplicated singleton pregnancies.What are the implications of these findings for clinical practice and/or further research? The study of abdominal pressure indicators such as intra-abdominal volume and compliance will help to a better understand the aetiology, pathophysiology, prognosis and treatment strategies for pregnant women with intra-abdominal hypertension.

LncRNA and transcriptomic analysis of fetal membrane reveal potential targets involved in oligohydramnios

Background

The multiple causes of oligohydramnios make it challenging to study. Long noncoding RNAs (lncRNAs) are sets of RNAs that have been proven to function in multiple biological processes. The purpose of this study is to study expression level and possible role of lncRNAs in oligohydramnios.

Methods

In this study, total RNA was isolated from fetal membranes resected from oligohydramnios pregnant women (OP) and normal amount of amniotic fluid pregnant women (Normal). LncRNA microarray was used to analyze the differentially expressed lncRNAs and mRNAs. Kyoto Encyclopedia of Genes and Genomes (KEGG) was used to analyze the main enrichment pathways of differentially expressed mRNAs. Real-time quantitative PCR (qPCR) was used to validate the lncRNA expression level.

Results

LncRNA microarray analysis revealed that a total of 801 lncRNAs and 367 mRNAs were differentially expressed in OP; in these results, 638 lncRNAs and 189 mRNAs were upregulated, and 163 lncRNAs and 178 mRNAs were downregulated. Of the lncRNAs, 566 were intergenic lncRNAs, 351 were intronic antisense lncRNAs, and 300 were natural antisense lncRNAs. The differentially expressed lncRNAs were primarily located in chromosomes 2, 1, and 11. KEGG enrichment pathways revealed that the differentially expressed mRNAs were enriched in focal adhesion as well as in the signaling pathways of Ras, tumor necrosis factor (TNF), estrogen, and chemokine. The qPCR results confirmed that LINC00515 and RP11-388P9.2 were upregulated in OP. Furthermore, the constructed lncRNA–miRNA–mRNA regulatory network revealed tenascin R (TNR), cystic fibrosis transmembrane conductance regulator (CFTR), ATP-binding cassette sub-family A member 12 (ABCA12), and collagen 9A2 (COL9A2) as the candidate targets of LINC00515 and RP11-388P9.2.

Conclusions

In summary, we revealed the profiles of lncRNA and mRNA in OP. These results might offer potential targets for biological prevention for pregnant women with oligohydramnios detected before delivery and provided a reliable basis for clinical biological treatment in OP.

Accuracy of the Ultrasound Estimate of the Amniotic Fluid Volume (Amniotic Fluid Index and Single Deepest Pocket) to Identify Actual Low, Normal, and High Amniotic Fluid Volumes as Determined by Quantile Regression

OBJECTIVES

To identify abnormal amniotic fluid volumes (AFVs), normal volumes must be determined. Multiple statistical methods are used to define normal amniotic fluid curves; however, quantile regression (QR) is gaining favor. We reanalyzed ultrasound estimates in identifying oligohydramnios, normal fluid, and polyhydramnios using normal volumes calculated by QR.

METHODS

Data from 506 dye-determined or directly measured AFVs along with ultrasound estimates were analyzed. Each was classified as low, normal, or high for both the single deepest pocket (SDP) and amniotic fluid index (AFI). A weighted κ statistic was used to assess the level of agreement between the AFI and SDP compared to actual AFVs by QR.

RESULTS

The overall level of agreement for the AFI was fair (κ = 0.26), and that for the SDP was slight (κ = 0.19). Although not statistically significant (P = .792), the positive predictive value to classify a low volume using the AFI was lower compared to the SDP (35% vs 43%). The positive predictive value for a high volume was higher using the AFI compared to the SDP (55% versus 31%) but not statistically significant. The missed-call rate for high-volume identification by the SDP versus AFI was statistically significant (odds ratio, 5.5; 95% confidence interval, 2.04-14.97). The missed-call rate for low-volume identification by the AFI versus SDP was not statistically significant (odds ratio, 3.3; 95% confidence interval, 0.96-11.53).

CONCLUSIONS

Both the AFI and SDP identify actual normal AFVs by QR, with sensitivity higher than 90%. The SDP is superior for identification of oligohydramnios, and the AFI superior for identification of polyhydramnios.

Advances in assessing body composition during pregnancy

The prevalence of excess gestational weight gain is increasing worldwide and is associated with pregnancy complications, including gestational diabetes mellitus, pre-eclampsia, preterm birth, macrosomia, and development of obesity in offspring. Whereas gestational weight gain positively correlates with the gain in fat mass (FM), fat-free mass (FFM) gain is relatively consistent across pregnancies. Commonly used methods to assess body composition include anthropometry, densitometry (air displacement plethysmography, underwater weighing), and hydrometry (isotope dilution, bioimpedance analysis). While these techniques can be applied to pregnancy, they require specific adjustments to assumptions inherent within each method, most importantly to accommodate for the hydration of FFM which is transient throughout gestation. Here we discuss the application of the abovementioned methods to pregnant women and the relevant adjustments needed to more accurately calculate FM based on body weight, body volume, or total body water. We also present a novel application of classical data to provide FFM density estimates for pregnant women at any stage of pregnancy. Use of these adjustments will help standardize assumptions on FFM hydration and minimize error in FM estimation. Techniques still fail, however, to fully distinguish tissue gains between mother and fetus. To fill this important gap, imaging techniques such as ultrasound and magnetic resonance imaging are being used more frequently and will provide more insight into fetal development, fetal adiposity, and depot specificity of maternal FM acquisition. Efforts to synchronize protocols are necessary to allow seamless comparison of data to advance the understanding of maternal body composition changes that contribute to pregnancy-related complications.