Measurement and evaluation of fetal fat layer in the prediction of fetal macrosomia in pregnancies complicated by gestational diabetes.

OBJECTIVES

To explore the predictive power of measuring the abdominal fetal fat layer (FFL) as a soft tissue marker at 31, 34, and 37 weeks' gestation to improve the detection of fetal macrosomia in pregnant women with GDM, in addition to the biometric values with close monitoring of maternal blood sugar level and BMI changes.

METHODS

We conducted a prospective observational study at the Department of Obstetrics, University Hospitals, Campus Kiel, Germany, in collaboration with diabetic clinic staff. Participants underwent a third-trimester scan and extra FFL measurements were performed at 31, 34, and 37 weeks of gestation. The clinical outcomes of pregnancy and birth weight were collected from the obstetric record. All of the enrolled women had an early pregnancy ultrasound scan to confirm gestational age.

RESULTS

The FFL at 34 and 37 weeks, with respective cutoff values of >0.48 cm and >0.59 cm, showed a very good sensitivity of 60% for both gestational points, and specificity of 89.3 and 90.6%, respectively. The probability of fetal macrosomia could be more than doubled if the FFL at 34 weeks was more than 0.48 cm. However, the probability of macrosomia dropped to 16% if the FFL was ≤0.48 cm. The median FFLs of macrosomic fetuses at 34 and 37 weeks were 0.50 (IQR 0.10) and 0.60 (IQR 0.25) cm, respectively. The mean age of the study population (n = 80) was 32.26 (SD = 5.06) years. In our study population, ten newborns were born with birth weight >4000 g. The body mass index (BMI) for the mothers of later-onset macrosomic newborns showed higher median values of 30 (IQR 8), 32 (IQR 5), and 33 (IQR 9) at 31, 34, and 37 weeks, respectively, in comparison to mothers of non-macrosomic newborn. However, the BMI did not show any statistically significant difference from those with normal-weight newborn and did not show any specific sensitivity for predicting macrosomia.

CONCLUSION

Measuring the FFL at 34 and 37 weeks of gestation, in addition to the standard measurement, might be useful for predicting macrosomia and is worth further evaluation.