A growth scan in pregnancy, also called the third trimester scan, is done in the last trimester to check the development and well-being of the baby. The ultrasound scan that produces a 2-D, black and white image of the baby is also done to determine the amount of amniotic fluid in the womb and position of the placenta. It can be done once or many times (as per the requirement). The first foetal growth scan is suggested between 28 weeks and 32 weeks of pregnancy to determine the foetal wellbeing. The second growth scan and colour Doppler studies are done closer to the due date, between 36 and 40 weeks.