THE POSSIBILITIES TO DETERMINE FETAL MATURITY BY ULTRASOUND DIAGNOSTICS

Background: Extragenital disorders in a pregnant patient, as well as complications of pregnancy often necessitate preterm delivery, when the state of the fetus is one of the criteria determining terms and type of delivery. In connection with this, the physician faces the challenge of accurate assessment of fetal maturity. 

Aim: To identify ultrasound signs of functional fetal maturity. 

Materials and methods: 120 pregnant patients were assessed at 35 to 40 weeks of gestation. Beyond a standard fetometry, we assessed interhemispheric cerebellar size, the biggest size of the Beclard’s nucleus, the ratio of cortical to medullar substance of fetal adrenal glands (adrenal coefficient), the ration between ultrasound density of lungs, liver and ultrasound density of fetal urine (histogram analysis). 

Results: Up to 36 weeks of gestation, the interhemispheric cerebellar size was below 52 mm, starting from 37 weeks, above 53 mm and from week 40 on, above 58 mm. All newborns, which had their interhemispheric cerebellar size ≥ 53 mm antenatally, were assessed as being mature at birth (p < 0.05). All newborns, which had Beclard’s nucleus size ≥ 5 mm antenatally, were assessed as being mature at birth (p < 0.05). At 35–35.6 weeks of gestation, mean adrenal coefficients in all cases exceeded 1. Starting with full 36 weeks of gestation onwards, this parameter decreased to 0.94 and showed a steady decrease thereafter. There were no signs of functional immaturity or respiratory distress among newborns with antenatal adrenal coefficient of ≤ 0.99 (p < 0.05). The ratio between ultrasound density of lungs to ultrasound density of bladder contents increases up to 37 weeks of gestation and remains stable up to 40 weeks. The ratio of liver density to the same substrate is non-significantly lower due to lower ultrasound density of the liver itself. The ratio of ultrasound density of the lung to that of the liver up to 36 weeks was at least 1.41 and decreased from 37 to 40 weeks of gestation. 

Conclusion: The fetometric parameter of interhemispheric cerebellar size has the maximal correlation with the term of gestation and can serve as an indirect measure of functional fetal maturity. The size of Beclard’s nucleus and adrenal coefficient may serve as parameters that most clearly reflect fetal tissue maturity and allow predicting respiratory distress in a newborn. Linear sizes of the adrenal gland can not serve as a maturity criterion due to high error of measurements, depending on the level of section by its height (pyramidal form). Despite an increase of the ratio of ultrasound density of the lung to that of the liver with longer term of gestation, it cannot be considered a reliable parameter of lung maturity after 35 weeks of gestation.