Association between amniotic fluid evaluation and fetal biometry: a prospective French "Flash" study

DNA concentrations in amniotic fluid according to gestational age and fetal sex: data from 2573 samples

PURPOSE

In some cases of prenatal genetic testing, an ample amount of fetal DNA is needed, to allow for parallel testing (conducting several genetic tests simultaneously). This study investigated the association between amniotic fluid DNA concentration and various factors. We aimed to define the required amount of amniotic fluid to be extracted in amniocentesis, to allow parallel testing throughout gestational weeks.

METHODS

DNA concentration was analyzed from amniocentesis samples taken during the years 2016-2022. Sex association was also analyzed in postnatal whole blood samples from a separate cohort. Theoretical minimum volume of amniotic fluid needed to ensure enough DNA for chromosomal microarray analysis and exome sequencing was calculated.

RESULTS

We focused our analysis on 2573 samples, which were taken during weeks 17-23 and 30-35. DNA concentrations increased from weeks 17 to 21, with relatively stable concentrations thereafter. Significantly higher DNA concentrations were seen in pregnancies of female fetuses. DNA concentrations in postnatal whole blood samples did not show this association. Across most weeks, the volume needed to extract 2 µg of DNA from 95% of the samples was about 34 ml.

CONCLUSION

DNA concentrations in amniotic fluid vary according to gestational age and are higher in pregnancies of female fetuses. This should be considered when determining the volume of fluid extracted and the timing of amniocentesis, with greater volumes needed in earlier stages of pregnancy.

Predicting the fetal weight by ultrasonography for isolated polyhydramnios: Comparison of 14 formulas

OBJECTIVE

To recalculate the estimated fetal weight (EFW) based on ultrasound measurements in patients complicated with isolated polyhydramnios, using 14 current formulas to observe which formula better predicts the EFW.

METHODS

This study examined pregnant women who gave birth in the hospital between January 2015 and January 2020. Maximum vertical pocket (MVP) was classified as, mild, moderate, and severe polyhydramnios, and the patients' measurements were reanalyzed using 14 formulas. The estimation of birth weight (EBW) alongside observed birth weight (OBW) facilitated the computation of statistical indices, namely the mean absolute percentage error (MAPE) expressed as [(EBW - OBW)/OBW × 100], the mean percentage error (MPE) denoted as (EBW - OBW)/(OBW × 100), and their corresponding 95% confidence intervals.

RESULTS

A total of 564 polyhydramnios patients were included in the study. When looking at the MAPE, the lowest rate (7.65) was found in the Hadlock 2 formula. Hadlock 1, Hadlock 3, and Shinozuka formulas demonstrated MAPE values most closely aligned with Hadlock 2. Weiner I and Thurnau were the formulas with the highest MAPE values. When the cut-off values for MAPE were taken as 10%, 4/14 of the formulas (Weiner I-II, Vintzleos and Thurnau) gave results above 10%. Among 14 formulas, 3 (21.4%) had positive (sonographic overestimation) (Hadlock 3, Shinozuka, and Vintzleos) and the other 11 (78.6%) had negative MPE (sonographic underestimation).

CONCLUSION

The Hadlock 2 formula had the lowest MAPE in predicting birth weight in patients with polyhydramnios, closely followed by the Hadlock 1, Hadlock 3, and Shinozuka formulas.

Evaluating the correlation between amniotic fluid volume and estimated fetal weight in healthy pregnant women

OBJECTIVES

The establishment of cut-offs for normal amniotic fluid volume (AFV) is valuable to predict perinatal outcomes. However, the most common methods to measure AFV are not accurate enough. It is important to understand factors that may be able to increase the accuracy of the calculation of AFV cut-off values. The objective of this study was to verify the correlation between AFV and estimated fetal weight (EFW).

METHODS

Records from almost 7,000 patients between 2012 and 2017 were accessed through hospital databases. The AFV measurements included in our analysis were obtained using the maximum vertical pocket technique.

RESULTS

AFV was positively correlated with EFW in the overall, male and female samples; however, the magnitude of the association was small (0.1

CONCLUSIONS

The incorporation of EFW together with other factors (e.g., gestational age, fetus sex) may increase the accuracy of the AFV cut-offs calculation and, ultimately, reduce morbidity.

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Key Words

• amniotic fluid
• estimated fetal weight
• maximum vertical pocket
• pregnancy complications

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MESH Headings

• Amniotic Fluid/diagnostic imaging
• Female
• Fetal Weight
• Gestational Age
• Humans
• Male
• Pregnancy
• Pregnant Women
• Prenatal Care
• Ultrasonography, Prenatal

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Affiliation(s)

Sara C S Souza OMNI Research Group, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada
Katherine Kim OMNI Research Group, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada
Alysha L J Dingwall-Harvey OMNI Research Group, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada
Romina Fakhraei OMNI Research Group, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada School of Epidemiology and Public Health, University of Ottawa, Ottawa, Canada
Yan Liao OMNI Research Group, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada
Laura M Gaudet OMNI Research Group, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Canada School of Epidemiology and Public Health, University of Ottawa, Ottawa, Canada Department of Obstetrics and Gynecology, Kingston Health Sciences Center, Kingston, Canada Department of Obstetrics and Gynecology, Queen's University, Kingston, Canada

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Correlation between newborn size and gross fetal movement as counted by a fetal movement acceleration measurement recorder

The development of the fetal movement acceleration measurement (FMAM) recorder has enabled the accurate counting of gross fetal movements. The aim of the study was to investigate whether gross fetal movement is related to a newborn's size. A total of 90 pregnant women who delivered singleton infant at term were recruited. Gross fetal movements were counted using an FMAM recorder during maternal sleep. The ratio of movement positive 10-s epochs to all epochs during one night was calculated as an index of fetal movement. Independent explanatory variables for the fetal movement index were selected from eight possibilities, that is, maternal age, gestational week, and the six physical measures of the newborn (height, weight, head circumference, chest circumference, Kaup index, and the ratio of head to chest circumference) with the stepwise regression procedure. The selected physical variables and the fetal movement index were analyzed using multiple regression analysis. A total of 2812.95 h from 423 night records were available. Gestational weeks and weight of the newborn were selected as the significant independent variables. Multiple regression analysis revealed that newborn weight had a positive correlation with the fetal movement index (p < 0.0001). The multiple regression equation was "The fetal movement index (%) = 34.9989-0.9088 × gestational weeks + 0.0033 × newborn weight (g)." A person's physical ability and lifetime activity level may originate from fetal health. This study may provide a new way of looking at the Developmental Origins of Health and Disease theory.

Comparison of automated vs. manual measurement to estimate fetal weight in isolated polyhydramnios

Objective To understand the impact of the measurement method to predict actual birthweight in pregnancies complicated with isolated polyhydramnios in the third trimester. Methods A prospective study was conducted with 60 pregnant women between the 37th and 40th weeks of gestation. Routine biometric measurements were obtained by two-dimensional (2D) ultrasonography. When a satisfactory image was obtained, the image was frozen to get two measurements. First, calipers were placed to get the manual measurement. Then automated measurement was captured by the ultrasonography machine in the same image. The fetal weight was estimated by using the Hadlock II formula. Results The mean difference was found to be 0.03, -0.77, -0.02 and 0.17 for biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL), respectively. Pearson's correlation coefficient between automated and manual estimated fetal weights (EFWs) and the actual birthweight was 0.919 and 0.796, respectively. The mean difference between actual and manual EFW measurement values was 46.16 ± 363.81 g (range between -745 g and 685 g) (P = 0.330). Also, the mean difference between actual and automated EFW measurement values was found to be 31.98 ± 218.65 g (range between -378 g and 742 g) (P = 0.262). The Bland-Altman test results have shown that, 666 g lower or 759 g higher values were obtained when the measurement was performed manually. On the other hand, EFW results were 396 g lower or 460 g higher than the actual birthweight with automated measurement tools. Conclusion The accuracy rate of fetal weight estimation with ultrasonography is high for both automated and manual measurements. Automated tools have a higher success to predict the EFW.