THIRD TRIMESTER SCREENING SCAN
The third trimester ultrasound scan is also called as Growth scan. This is usually done at 30 to 37 weeks. This is an optional scan and may be suggested by your O&G doctor over the pre-natal check-ups. A Doppler scan will be done to assess the blood flow in the umbilical cord uterine artery and middle cerebral artery.
The scan takes about 30 minutes, depends on the fetal position.
The following details are assessed at this scan:
a) Measurements of head circumference, abdominal circumference and femur length to
check if the biometric measurements of the fetus are appropriate for the gestational
age of the fetus.
b) Detection of some late onset structural abnormalities (1:200 abnormalities are
detected after a normal first and second trimester scan).
c) Doppler studies of the uterine, middle cerebral and umbilical arteries. Calculation of the cerebroplacental ratio from 36 weeks onwards may be useful in timing the
delivery of the fetus. Measurement of the uterine artery Doppler on the recently
implemented module on the Astraia program that the clinic uses allows the risk
assessment for pre-eclmapsia before 36 weeks and at term.