Detection of the small-for-gestational age twin fetus by a two-stage ultrasound examination schedule.

Serial ultrasonic measurement of the biparietal diameter is an unsatisfactory means of detecting the small-for-gestational age (SGA) fetus in twin pregnancies. A new two-stage ultrasound examination schedule, highly effective in detecting the SGA singleton fetus, has been evaluated prospectively in 31 twin pregnancies. The schedule comprises ultrasonic assessment of gestational age in early pregnancy, followed by measurement of the product of the crown-rump length and trunk area of both fetuses at 34-36 weeks. All Nineteen SGA twin fetuses were detected using this schedule; the technique offers several other advantages over serial biparietal cephalometry.