Ultrasonography diagnosis

Fetal growth is a dynamic process determined by a combination of genetic, intrauterine, and environmental influences. However, assessment of fetal growth with a onetime measurement is standard clinical practice, despite recognition that a single measurement can only indicate size, not growth. For this purpose, the fetal biometric measurements commonly used are biparietal diameter, head circumference, abdominal circumference, and femur length. These measurements can be combined into an estimated fetal weight using various formulae to provide a more straightforward and clinically relevant estimate of fetal growth. There are many published fetal growth charts available, and the choice of chart used also requires careful consideration as several potentially confusing terms and concepts associated with fetal size and growth are reported in the literature: fetal growth “standards,” fetal growth “references,” customized charts, and growth velocity standards. The relative merits and disadvantages of each approach are discussed, although none has so far proved to be clearly superior to the others. As for the timing of third trimester ultrasound screening for term fetal growth restriction, which is not currently recommended in most countries, recent studies of high methodological quality suggest that ultrasound assessment at 35–37 weeks performs better than at 30–32 weeks.