Ultrasound in pregnancy
Ultrasound imaging or sonography is based on the priciple of piezo-electric effect.Sound waves are produced by a piezoelectric crystal and images are produced by sound waves being reflected by various organs in the body.It does not use any ionizing radiation.
Doppler US can also be used especially in high risk mother like Pregnancy induced hypertension and IUGR to assess utero-placental and fetal blood flow dynamics.
Please note-ultrasound cannot identify all fetal abnormalities. It can determine the sex of the baby (but telling the sex of the baby is illegal in India!!)