Morphological and functional evaluation of normal and abnormal fetal growth by ultrasonography.

Correction or estimation of gestational age is essential for the evaluation of fetal growth. When necessary, an appropriate fetal biometric parameter should be selected depending on fetal size. In the first trimester, crown-rump length (CRL) is appropriate, especially when the CRL is 20-40 mm. In the second trimester, biparietal diameter (BPD), head circumference (HC), and femur length (FL) are of equal predictability. Fetal weight estimation is still the basis of evaluation of fetal growth. The most predictable formula currently available includes the parameters BPD (or HC), abdominal circumference (AC), and FL. Serial measurements of AC are useful for diagnosis of intrauterine growth restriction (IUGR) and macrosomia. Quantitative evaluation of soft tissue deposition may be informative for macrosomia. Functional evaluation using Doppler velocimetry is essential in IUGR cases associated with uteroplacental insufficiency. Analysis of blood velocity waveforms of the umbilical and intracranial arteries, predominantly the middle cerebral artery, is widely performed. An increase in the pulsatility index (PI) or resistance index (RI) of the umbilical artery and/or a decrease in the PI or RI of the middle cerebral artery are highly predictable for fetal hypoxia and/or acidosis.