Ultrasound-determined fetal subcutaneous tissue thickness for a birthweight prediction model

A Nomogram of Lateral Abdominal Wall Fat Thickness in Normal Third Trimester Fetuses

OBJECTIVES

The objective of this study is to establish a nomogram of fetal abdominal wall fat thickness in fetuses with known normal neonatal outcomes.

METHODS

After IRB approval (HSD-49496), 157 ultrasound examinations in 100 patients, 41 of whom had multiple examinations during the same pregnancy were reviewed. The thickness of the fetal lateral abdominal wall fat Interreader agreement was summarized using the intraclass correlation coefficient (ICC). Fat thickness growth curve equations were estimated to quantify the relationship between fat thickness and gestational age.

RESULTS

The abdominal wall fat had an intraclass correlation coefficient of 0.93 (95% confidence interval, 0.90-0.96) for 2 readers. Fat thickness increased in all 41 fetuses with multiple examinations (P < 0.001). Fat thickness increased 0.19 mm per week on average (95% confidence interval, 0.17-0.21 mm; P < 0.001) from an average of 1.7 mm at 22 weeks and 4.3 mm at 36 weeks.

CONCLUSIONS

Lateral wall abdominal fat can be reproducibly measured with good inter observer correlation, and fat does increase with increasing gestational age in normal fetuses. We believe the utility of fetal fat is the documentation of its presence as a reassuring finding indicative of normal fetal health, particularly when prior dating is discrepant or not available during the third trimester.

Altered maternal and placental lipid metabolism and fetal fat development in obesity: Current knowledge and advances in non-invasive assessment

Abnormal maternal lipid profiles, a hallmark of increased maternal adiposity, are associated with pregnancy complications such as preeclampsia and gestational diabetes, and offspring long-term metabolic health is impacted as the consequence of altered fetal growth, physiology and often iatrogenic prematurity. The metabolic changes associated with maternal obesity and/or the consumption of a high-fat diet effecting maternal lipid profiles and metabolism have also been documented to specifically affect placental function and may underlie changes in fetal development and life course disease risk. The placenta plays a critical role in mediating nutritional signals between the fetus and the mother. As obesity rates in women of reproductive age continue to increase, it is becoming evident that inclusion of new technologies that allow for a better understanding of early changes in placental lipid transport and metabolism, non-invasively in maternal circulation, maternal tissues, placenta, fetal circulation and fetal tissues are needed to aid timely clinical diagnosis and treatment for obesity-associated diseases. This review describes pregnancy lipid homeostasis, with specific reference to changes arising from altered maternal body composition on placental and fetal lipid transport and metabolism. Current technologies for lipid assessments, such as metabolomics and lipidomics may be impacted by labour or mode of delivery and are only reflective of a single time point. This review further addresses how established and novel technologies for assessing lipids and their metabolism non-invasively and during the course of pregnancy may guide future research into the effect of maternal metabolic health on pregnancy outcome, placenta and fetus.

Abdominal subcutaneous and visceral fat thickness in newborns: correlation with anthropometric and metabolic profile

OBJECTIVE

To correlate abdominal subcutaneous and visceral fat thickness with anthropometric data and metabolic profile in newborns.

STUDY DESIGN

A cross-sectional study with 99 newborns was performed at Instituto de Medicina Integral Professor Fernando Figueira, Brazil. Abdominal subcutaneous and visceral thickness were measured by ultrasound. Glucose, insulin, homeostatic model assessment-insulin resistance (HOMA-IR), total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol and triglycerides were determined. Pearson correlation coefficients were calculated.

RESULT

Abdominal subcutaneous fat thickness was positively correlated with birth weight (r=0.31; P<0.001), height (r=0.27; P<0.001) and abdominal circumference (r=0.26; P<0.001), but not with metabolic profile. Abdominal visceral fat thickness was correlated with abdominal circumference (r=0.23; P=0.01), insulin (r=0.21; P=0.04) and HOMA (r=0.24; P=0.02). The results remained the same among males and females.

CONCLUSION

Abdominal fat distribution in newborns has a different correlation with anthropometric and metabolic profile. Abdominal subcutaneous fat thickness is positively correlated with anthropometric data whereas abdominal visceral fat thickness is correlated with insulin and HOMA-IR.

Longitudinal measurement of fetal thigh soft tissue parameters and its role in the prediction of birth weight

OBJECTIVE

The aim of this study was to profile longitudinal changes in thigh muscle and fat with gestation and to determine whether thigh measurements can improve the prediction of birth weight (BW).

METHODS

A prospective longitudinal study of subcutaneous soft tissue measurements was conducted in 328 singleton fetuses at 28 and 37 weeks gestation. Estimated fetal weight (EFW) was calculated using abdominal circumference, femur length, biparietal diameter, and head circumference.

RESULTS

The fetal abdominal subcutaneous tissue (FAST) and thigh muscle and fat show an increase with gestation. At 28 weeks gestation, the abdominal circumference, thigh fat, FAST, and EFW percentile were found to be significant predictors of BW. A combination of EFW percentile and thigh fat were found to be the optimal multivariate model at 28 weeks for predicting BW. At 37 weeks, BW prediction using EFW percentile, FAST, and thigh fat was the most accurate. The results revealed acceptable reproducibility for fetal thigh muscle and fat.

CONCLUSION

This study provides reference ranges for thigh fat and muscle at 28 and 37 weeks gestation. The inclusion of fetal thigh fat in the algorithm improves the predictive power for birth weight. This information is important to explore the role of fetal thigh in the detection of aberrant growth.

Quantification of the subcutaneous fat layer with MRI in fetuses of healthy mothers with no underlying metabolic disease vs. fetuses of diabetic and obese mothers

OBJECTIVE

To assess the age-dependent fetal subcutaneous fat layer (SCFL) of non-diabetic, normal-weight mothers and fetuses of mothers with gestational diabetes (GDM) and normal body weight or obesity.

METHODS

In a prospective study, we evaluated 115 MRI examinations of fetuses with no history of (maternal) metabolic disease [gestational week (GW) 29 to 39/40] and 50 examinations of mothers with GDM and normal body weight or obesity. The SCFL was measured at predetermined anatomical landmarks. Measurements were correlated with the maternal body mass index (BMI) and glycated hemoglobin A1c (HbA1c)-values in diabetic mothers.

RESULTS

In fetuses of non-diabetic, normal-weight mothers, measurements showed high consistency within the respective GW and ranged from 2 mm at GW 29 at all measured points, up to 4.5 mm at the trunk and 6.0 mm at the extremities at GW 39/40. In 47/50 fetuses of mothers with GDM, the SCFL was within the range of fetuses of mothers with no metabolic disease. In three patients with GDM and BMI<30, the SCFL-thickness was decreased. No fetuses showed an increased SCFL-thickness.

CONCLUSION

The SCFL of normally developed fetuses is easily detectable from GW 29 on T1-weighted images (T1-W), and increases with gestational age. The presented data provide physiological benchmarks to evaluate developmental status and may help in the prenatal diagnosis of abnormal growth and macrosomia. In pregnant women with well-controlled GDM, an increase of the SCFL is not expected.

A new algorithm for improving fetal weight estimation from ultrasound data at term

Objective

The purpose of this retrospective study was to find a method of improving the accuracy of fetal birth weight estimation on the basis of traditional ultrasonographic measurements of the head, thorax, and femur at term. In this context, we analyzed a novel regression method comparing to existing algorithms.

Methods

The delivery records of two hospitals were searched for women who delivered macrosomic infants, and the patients’ medical records were retrospectively reviewed in order to derive clinical and ultrasonographic data at term. A total of 223 patients with macrosomic infants (birth weight > 4,000 g) were identified. These patients were complemented by data for 212 women who had ultrasound fetal assessments of less than 4,000 g. We used the method of isotonic regression to construct a birth weight prediction function that increases monotonically with each of the input variables and which minimizes the empirical quadratic loss.

Results

A suspicion of macrosomia was based on a history of macrosomia, fundal height, and sonographic weight estimation >4,000 g. The mean period between ultrasound weight estimation and delivery was 7.2 days. The ability of the biometric algorithms developed to predict fetal weight at term ranged between a mean absolute error of 312 and 344 g, given a confidence interval of 95%. We demonstrate that predictions of birth weight on the basis of ultrasound data can be improved significantly, if an isotonic regression model is used instead of a linear regression model.

Conclusions

This study demonstrates that ultrasound detection of macrosomia can be improved using the isotonic regression method.