Final answer:
Ultrasounds are performed throughout pregnancy to monitor fetal growth and development. They are used to assess organ development in the first trimester, monitor the fetus's health in the second trimester, and evaluate fetal growth and position in the third trimester. They can also be used postpartum to check for retained placenta.
Step-by-step explanation:
Ultrasounds are performed throughout pregnancy to monitor fetal growth and development. In the first trimester, ultrasounds are used to assess organ development and determine the gestational age of the fetus. During the second trimester, ultrasounds help in monitoring the fetus's health and detecting any potential abnormalities. In the third trimester, ultrasounds are used to evaluate fetal growth and position. They can also be used after childbirth to check for retained placenta.